Editor's note: This story originally ran on the 50th anniversary of JFK's assassination.

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It has been more than half a century, and so many lifetimes ago. Yet the images from November 1963 remain haunting, blurred into our national consciousness. Sixty years later, CBS News relives that drama, moment by moment, as it unfolded before a world in shock.

Bob Schieffer | CBS News: When the president came to Texas, I was a young newspaper reporter covering the crime beat for the Fort Worth Star Telegram. With JFK and his elegant wife Jackie heading our way, for us it was the biggest story of the year. Little could we know history was about to be made. Time stopped cold, in that dark moment, on a Dallas street. The horror of the assassin's shots shattered dreams and echoed through the decades, coloring our politics, and lives. It was also a watershed moment for American television news, led by CBS News anchorman Walter Cronkite. With the death of a president came the birth of live coverage. America shared a national tragedy, as it happened.

Because of television we thought we knew JFK and his family more intimately than any of his predecessors, the man friends simply called "Jack."

Voice of John F. Kennedy: I was born in Boston, Massachusetts in 1917. I have eight brothers and sisters and they... I'm the second oldest, And it was a great pleasure growing up in a large family. I think it makes a tremendous difference.

Voice of Rose Kennedy: His father would go out and watch the sailboats ... and then he'd say, "Why are your sails flapping while the other one was straight? And the other one won the race and you didn't. ... If you're gonna race, why, do it right and come in a winner. Second place is no good."

Sandy Socolow | Walter Cronkite's producer: John F. Kennedy ... was brought up in an ultra-rich way. Very well educated. ... Very good-looking. Very personable. ... He was extraordinarily self confident.

Schieffer: Sure, he was playing the media. ... But the fact is he was just so good at it, that it worked. ... And who could blame him?

1960 Kennedy-Nixon presidential debate rehearsal:

Kennedy: It's a pleasure to be here tonight to participate in this program which opens up a series of discussions. ... Is that about the right tone of voice?

Richard Nixon: Think I better shave.

Walter Cronkite on the air, 1960: And the popular vote ... 84 percent of the precincts counted now ... give Kennedy just a little margin over 50 percent of the vote... Nixon almost 50 percent of the vote. One of the closest elections in our nation's history has been recorded in this year of 1960.

Walter Cronkite | CBS News (1993): Kennedy seemed to be leading us into a new era of, of youthful exuberance ... over the fun of life, the fun a country could have being itself, being important in the world. We were dancing on clouds.

Schieffer: It was just the difference in night and day. He was the Technicolor President, and we had sort of seen the presidency in black-and-white up until that point. ... Suddenly we had this young handsome president and this gorgeous wife and these beautiful children ... and he is the first president that we came to really know, and we came to know his family and that was because of television.

Schieffer: In those days presidents didn't travel very much and it was a major event. ... They decided to come to Texas because they thought they could raise money there. ... The people were so excited.

Schieffer: The relationship between Lyndon Johnson and John Kennedy was very complex. They were partners. Were they ever friends?

Robert Caro | Author and historian: Not really.

Friday, Nov. 22, 1963

Schieffer: They decided to fly from Fort Worth to Dallas, which is literally only 30 miles. They flew over. Air Force One lands at Love Field.

Bob Huffaker | Former KRLD radio reporter: Well the day began gray and cold ... there was a misting rain falling and the temperature was cold. Suddenly at mid-morning the skies opened up and it was a beautiful ... blue, spring-like day.

Caro: We see it, the great plane is gleaming silver in the background, everything is bright under a bright Texas sun, and you hear the television announcer: "There she is..."

Reporter: ...and there's Mrs. Kennedy, the first lady stepping from the plane. Wearing a bright pink suit with a dark fur collar and a matching pink hat, and the president wearing a dark suit.

Caro: They hand Jackie at the bottom of the stairs this bouquet of roses.

Reporter: She does makes a very striking picture as she clutches the huge bouquet of bright red roses...

Caro: He takes Jackie and they walk along the fence. And someone said there was no brighter moment in the Kennedy presidency then that moment at Love Field in Dallas.

Schieffer: They decided because the skies had cleared to take the bubble-top off the presidential limousine.

Reporter: And the president will be riding in the open. ... That car was flown in here last night from Washington...

Huffaker: The crowd cheered as the president and his beautiful wife came past us.

Reporter: And now the ticker tape and uh ... other confetti and such is beginning to flow from the windows and the crowd at our point is surging forward. There is a big cheer going up...

Schieffer: As they turned to go into the main downtown area, Nelly Connally, who was John Connally's wife, [Texas] Governor Connally's wife, turned to the president and said, "Well, Mr. President, you can't say Dallas doesn't love you."

Reporter: ... and here is the President of the United States ... and what a crowd... what a tremendous welcome he is getting now.

Huffaker: The crowd just surged out from their points on the sidewalk and filled the street from curb to curb.

Caro: Then they turn off Main Street into this open grassy area, Dealey Plaza, and there's a sharp cracking sound. ... John Connally, I remember saying to me, "I was a hunter. I knew the moment I heard it, it was the crack of a hunting rifle."

Abraham Zapruder film: I was down on this freeway early ... and even the freeway was jammed pack with spectators waiting their chance to see the president as he made his way toward the trade mart ... it appears as though something has happened in the motorcade route ... something I repeat has happened in the motorcade route.

Schieffer: Well, it was just pandemonium. It was just a terrible moment.

Caro: So the three cars — the cars with President Kennedy, the Secret Service car and Johnson's car squeal up the ramp to an expressway ... and then off the expressway and into the emergency bay at Parkland Hospital.

Reporter: There has been a shooting ... Parkland Hospital has been advised to stand by for a severe gunshot wound.

Cronkite (1993): Looking right at it when the bells rang, five bells for a bulletin. ... Shots rang out while the president's motorcade drove through the streets of Dallas. ... And with that I turned around and shouted, "Let's get on the air, lets get on the air!" Well. in those days we didn't keep a camera hot.

Socolow: And he couldn't get on the air on television. You never saw Cronkite. You saw a card on the screen.

Cronkite on the air: Here is a bulletin from CBS News. In Dallas, Texas, three shots were fired at President Kennedy's motorcade in downtown Dallas.

Huffaker: This was the day that the news went live on television.

Cronkite on the air: The first reports say the president, Kennedy has been seriously wounded by this shooting.

Schieffer: People were crying. People were just walking around with a blank look on their face. "What does this mean? What's happened?"

Walter Cronkite on the air: This is Walter Cronkite in our newsroom. There has been an attempt, as perhaps you know now, on the life of President Kennedy. He was wounded in an automobile driving from Dallas Airport into downtown Dallas, along with Governor Connally of Texas. They've been taken to Parkland Hospital where their condition is as yet unknown.

Dr. Kenneth Salyer: I'm Dr. Kenneth Salyer. And on Nov. 22, 1963, I was on neurosurgery call at Parkland Memorial Hospital in Dallas, Texas. ... A nurse ran into the room and said "the president's been shot."

Schieffer: And what did you do?

Dr. Salyer: When I walked in, my colleagues were at the top of the table in Trauma Room One. ... The president ... had a large, huge jagged injury of the right side of his skull, with pieces missing.

Schieffer: Was he alive?

Dr. Salyer: He was still breathing ... and we were trying to intubate him, get a tube into his windpipe, trachea. ... But it wouldn't go past this wound.

Cronkite on the air: We have not been told their condition. At Dallas, in a downtown hotel room, a group had been gathered to hear President Kennedy and was waiting his arrival. Let's switch down there now where Eddie Barker of KRLD is on the air.

Eddie Barker reporting: As you can imagine there are many stories that are coming in now as to the actual condition of the president. One is that he is dead. This cannot be confirmed.

Schieffer: Did you think this was survivable?

Dr. Salyer: I didn't make that assessment at the moment I was taking care of him. ... This is a major, high velocity injury.

Huffaker: As I was standing in the crowd, two priests brushed past me...

Voice of Bob Huffaker | KRLD Radio: President Kennedy is on the inside of Parkland Hospital and two priests have just been sent in to the room with the president.

Dr. Salyer: As I looked up in the room, in the far back of the room is Mrs. Kennedy ... blood splattered on her dress. But she was just observing everything, wasn't talking.

Cronkite (1993): My God — who, what, why? Surely the president won't die. I mean, that can't be. He won't die, surely.

Schieffer: How long did that go on?

Dr. Salyer: It seemed like forever. But it was really probably less than 30 minutes.

Cronkite on the air: From Dallas, Texas, the flash, apparently official: President Kennedy died at 1:00 p.m. Central Standard Time, 2:00 Eastern Tme, some 38 minutes ago. [Takes off glasses, pauses.]

Socolow: He stopped in his tracks. ... tough man who understood the momentousness of what he was charged with doing.

Cronkite (1993): It was disbelief that it could have happened, that it had happened.

Dr. Salyer: As I was looking at Mrs. Kennedy and everyone started to exit the room and she came over. We had covered him up ... and she laid on his chest. And took a ring off, and put onto his finger. ... And I thought it was a very touching moment.

Socolow: As the news spread people stopped what they were doing to go to the radio, mostly, but also to television. ... It was the first instance of wall-to-wall news coverage.

Dr. Martin Luther King Jr.: It was one of the most shocking things I'd ever heard. Frankly, I was very upset and couldn't adjust to it and could hardly believe it in the beginning.

Penny Robinson to Charles Kuralt: Nobody could believe it. It's too... there's no words to express what happened at all.

Charles Kuralt | CBS News 1963: It's true that there are no words to express it and that feeling is obvious all around us on the streets of Los Angeles.

Richard Nixon: Today millions of people throughout the world are trying to find words adequate to express their grief and their sympathy to his family.

Man on the street, NYC: We are sorry. Deeply moved over this incident. This is a dark day in the history of America.

Edward Kennedy: I do want to say how appreciate both my parents have been for the tremendous outpouring of thoughtfulness and prayers that have come from all Americans from all parts of the country.

Man on the street: Someone to do this must be mentally deranged. No clear-thinking human person would ever think of doing something like that.

Dan Rather | CBS News Dallas reporting: These are scenes at a building across the street from the scene where President Kennedy was shot. ... Some empty cartridges have been found in that building. ... Perhaps out of one of those open windows is where the assassin of President Kennedy is believed to have fired the fatal shots.

Dan Rather (2008): After the initial hammer to the heart that an assassination of the president — the reality of that sinks in, then it was, "focus on the story." Because if you don't do that, then you're at some risk of just falling apart emotionally.

Cronkite on the air: In Dallas— a Dallas policeman just a short while ago was shot and killed while chasing a suspect.

Schieffer: And a policeman named J.D. Tippit saw a man walking down the street. And called him over to the police car. And when he did, Oswald walked up and shot him at point-blank range.

Dan Rather reporting: This is 24-year-old Lee H. Oswald. ... Now here is the gun police say was used to kill the president. ... Oswald first was charged with killing the policeman, police say that have at least one eyewitness to that.

Oswald: I really don't know what this situation is about. Nobody has told me anything except I'm accused of, uh, murdering a policeman.

Reporter: Did you kill the president?

Oswald: No, I have not been charged with that. In fact nobody has said that to me yet. The first thing I heard about it was when the newspaper reporters in the hall asked me that question.

Schieffer: And I drove down to The Star Telegram. ... And a woman called in and said, "Is there anyone there who can give me a ride to Dallas?" And I said, "Well, lady, you know, we're not running a taxi here. And beside, the president has been shot." And she said, "Yes ... I think my son is the one that they've arrested."

Marguerite Oswald: I spoke a few words to Lee and he says, "Mother don't worry about a thing..."

Schieffer: And it was Lee Harvey Oswald's mother, Marguerite Oswald. We wrote down the address, and went out and picked up her. And we drove her to Dallas. ... It was my first really big scoop.

Caro: The agents say to [Lyndon] Johnson, "We've gotta get out of here." Johnson says, "No, I'm not leaving without Mrs. Kennedy." They say to him, "Mrs. Kennedy won't leave without her husband's body." He says, "then we'll go to Air Force One and we'll wait there until she comes aboard with the coffin. But I'm not leaving Dallas without her."

Dan Rather reporting: Mrs. Kennedy, back the way she had come, in an ambulance now which bore her husband's body.

Caro: When they get Johnson on the plane they draw the window shades. They're afraid of snipers. Nobody knows at this moment if this was the beginning of a conspiracy.

Schieffer: Air Force One is still on the ground at Love Field. Johnson has literally taken command?

Caro: He walks into the center of the room and begins giving orders ... who he wants there. Particularly he wants Mrs. Kennedy there.

Cronkite on the air: We just got word from our reporters out there at the airport ... that Lyndon B. Johnson has been sworn in as the President of the United States.

Caro: Mrs. Kennedy has come aboard with her husband's coffin, and it's put in the rear section.

Schieffer: Mrs. Kennedy would not change clothes. She said, "I want them to see what they have done to him."

Caro: Lady Bird Johnson says, "That immaculate woman — her skirt was caked with blood." And Lyndon Johnson asks her to be present at the ceremony, and she was to say, "For the sake of history I should."

Schieffer: The picture said exactly what Johnson wanted it to say. And that is: "The United States is still on course. We have had the death of a president. But the country and the constitution still lives."

A new president: LBJ

Robert Caro: Lyndon Johnson takes the oath of office on Air Force One. His hand comes down, he says: "Now let's get airborne." On this flight across the United States, you have this plane carrying two presidents, one dead and one alive. No matter how long America's history is, this will always be one of the most dramatic and defining moments in it.

Reporter: President Lyndon Johnson has arrived at Andrews Air Force Base in Maryland. This is film, or tape, of that arrival. (Background: "Live, live, live!") It is live. It is live, right now.

Caro: And this great silver plane comes gliding out of the darkness.

Reporter: This is one of the most unique and tragic moments in the history...

Caro: The minute the front door opens, Robert Kennedy runs up the front steps to the plane. Pushes past Lyndon Johnson without even looking at him. Doesn't acknowledge him. And, comes up to Jackie, and says, "Jackie, I'm here."

Reporter: I'm watching a turnover in government, at the highest office. And now we can see what we believe to be a coffin containing the body of President Kennedy being moved from Air Force One.

Caro: And when the coffin comes out, right behind it, are Jackie Kennedy and Bobby Kennedy.

Reporter: This is a scene at Andrews Air Force Base. With a casket of— carrying the body of President Kennedy is being transferred to an ambulance.

Socolow: Nobody understood, at the time, what this event meant for television news. Television news, suddenly became important.

Reporter: Behind it comes, Mrs. Kennedy and Robert Kennedy.... And now President Johnson is coming down the ramp, out the back door.

Schieffer: Johnson had this innate sense of command. He knew that the country had to know that there was continuity. It was a sad moment, but it was a great moment in the history of the country because it said: there is still a president.

Caro: There is no presidential podium, there's no presidential seal, all they've done is put this bunch of microphones on the bare tarmac.

President Lyndon Johnson: We have suffered a loss that cannot be weighed. For me, it is a deep personal tragedy. I know that the world shares the sorrow that Mrs. Kennedy and her family bear. I will do my best, that is all I can do. I ask for your help ... and God's.

Schieffer: The speech was poignant, but it was brilliant in its brevity.

Cronkite (1993): We had a whole new world out there. Lyndon Johnson was not going to be John Fitzgerald Kennedy by any means.

Reporter: At 4:30 this morning Mr. Kennedy's body was returned to the White house. George Herman was on hand when it arrived.

George Herman reporting: President John F. Kennedy comes back to the White House for the last time.

Cronkite on the air: There will be a particularly poignant time for the Kennedy family next week.The two Kennedy children, uh, both have birthdays next week. John, 3, November the 25th, and Caroline, 6, on November the 27th. An entire nation has almost come to a stop today, uh, in the wake of the horrible news.

Huffaker: I had never seen anything like I saw when I arrived on that Saturday morning after the assassination. The entire hallway was filled with, probably, perhaps as many as a hundred reporters.

Cronkite on the air: We reported to you on the arrest of that individual in Dallas. He is being grilled now. He is said to be 24 years old. The name has been given for him by Dallas Police as Lee H. Oswald.

Reporter: Has he confessed sir? Has he made a statement?

Official: He has not confessed.He has made no statement. Charges of murder have been accepted against him.

Dan Rather reporting: Oswald has admitted nothing. After further questioning, he was formally charged with the president's death. That gun is a powerful military rifle, which police found in the building from which the president is believed to have been shot.

Schieffer: Lee Harvey Oswald was on the sixth floor of the Texas School Book Depository when he shot the president. He had a birds-eye view. If you go and look out that window, where he was, you realize you didn't have to be a very good shot.

Dan Rather reporting: Lee Oswald, espouser of leftist causes: an active member of the Fair Play for Cuba Committee, an avowed admirer of Russia and of Cuba's Fidel Castro, a man who once lived in Russia.

Reporter: What did you do in Russia?

Oswald: A policeman hit me.

Huffaker: We knew that Oswald was the most hated suspect of the 20th century.

Reporter: Chief, do you have any concern for the safety of your prisoner In due of the high feeling among the people of Dallas over the assassination of the president?

Police Chief: No, but precautions ... necessary ... precautions will be taken, of course.

Schieffer: On that Sunday, the plan was to transfer Oswald from the Dallas City Jail, where he had been questioned and where he had been kept, and transfer him to the county jail.

Harry Reasoner, CBS News, on the air: This is how things stand at this hour. In Washington, it is not long until the time for the transfer of the body of President Kennedy from its repose at the White House to the rotunda of the Capitol where it will lie in state. In Dallas, Lee Oswald, the man accused of the assassination of the president, is to be moved from one jail to another. We will have a direct report.

Rather (2008): This was something ... brand new. Covering this kind of tragedy, nobody had done it on television before.

Harry Reasoner on the air: Let us go now to the White House and Robert Pierpoint.

Dan Rather (2008): Nobody knew how to do it, and in terms of coverage ... everybody in television ... we were making it up as we went along.

Harry Reasoner on the air: We are now switching to Dallas where they are about to move Lee Oswald and where there is a scuffle in the police station...

Reporter: We are going to switch now to Bob Huffaker, down in the basement of the courthouse, who is close to the scene. Go ahead, Bob.

Bob Huffaker: Lee Harold Oswald has been shot. The situation is now that Lee Harold Oswald has been shot. The man who saw the shot fired, said it was fired by a man wearing a black hat, a brown coat...

Huffaker: I had looked and seen Oswald grimace, grasp his stomach and fall. And I knew, that, what we had feared, had actually taken place.

Harry Reasoner: We have, we got our tape. We have re-racked the video tape that shows that whole scene of confusion.

Schieffer: Suddenly, these two detectives walk out, with Oswald between them, and someone just walks up and sticks a gun in Oswald's side and shoots him.

Schieffer: And again it's just this total, what in the world happened? How could this have happened?

Socolow: From a journalist's point of view, there were so many questions to be answered. Who was the murderer? Why did he do it?

Reporter: And you knew him?

Officer: Yes, sir.

Bob Huffaker: And he is a resident of Dallas, is he not?

Officer: Yes, sir.

Cronkite (1993): The police, uh, captured a man at the scene who reporters saw shoot Oswald and have booked him.They say his name is Jack Ruby, or Rubenstein.

Huffaker: The operator of a seedy strip club in downtown Dallas.

Bob Huffaker reporting: Here comes Oswald, he, he is ashen and unconscious ... and now the ambulance is coming out ... the ambulance with Lee Harvey Oswald, who was shot.

Cronkite (1993): He was taken to Parkland Hospital and died an hour and 15 minutes after he was shot, in a emergency room just 10 feet from the room where President Kennedy had died almost exactly 48 hours before.

Schieffer: That weekend was unlike anything that had ever happen in television or in journalism, uh, in this country. I never felt that way until 9/11.

Did Oswald act alone?

Bob Schieffer: The day Oswald was to be transferred to the county jail in Dallas, I was sent to cover his arrival. As we know he never got there. Instead, his murder fueled a firestorm of suspicion about a possible conspiracy. Was Jack Ruby sent to silence the president's assassin? Even after all these years, a [2013] CBS News poll shows most Americans — 61 percent — don't believe Lee Harvey Oswald acted alone.

Reporter: It appears as though something has happened in the motorcade route — something, I repeat, something has happened in the motorcade route.

Schieffer: From the moment the sound of those shots were heard, people began to wonder ... was there a conspiracy?

Reporter: Parkland Hospital has been advised to stand by for a severe gunshot wound...

Schieffer: Those who were down on Dealey Plaza ... didn't know what had happened.

Reporter: Something is wrong here, something is terribly wrong...

Caro :It's an atmosphere of uncertainty. As Air Force One is heading to Washington, the Mexican border is being sealed because we're afraid of conspirators getting away.

Philip Shenon: Within hours of the assassination, Bobby Kennedy took the director of the CIA out on to his lawn and asked the question bluntly, "Did you kill my brother?"

Schieffer: And his answer?

Shenon: His answer was no.

In his account of the Kennedy assassination, Philip Shenon, a former investigative reporter for The New York Times, explores why many suspected an international conspiracy.

Shenon: There was terrible suspicion at that time about the Soviet Union, about Cuba, about the larger Communist threat. ... Fidel Castro knows, in the fall of 1963, that the Kennedy administration is trying to kill him. And so ... it was an obvious suspicion that Castro would be involved in Kennedy's death.

Before the week was out, President Johnson decided that to quell America's fears, a high level commission to investigate the assassination was necessary.

Reporter: The seven members of the Warren Commission, headed by the Chief Justice of the Supreme Court...

Shenon: In September 1964, after... 10 months of investigation ... the Warren Commission determined ... that there was no evidence of a conspiracy and that it appeared Lee Harvey Oswald was the lone gunman in Dealey Plaza.

Yet the Warren Commission itself would come under intense scrutiny. Four separate government investigations, 33 television reports from CBS News alone, and of course, Hollywood.

After all these years, what do we finally know? Was the president really killed by a lone gunman in Dealey Plaza?

The best record of the assassination to stand the test of time is Abraham Zapruder's famous 26 ½ seconds of 8mm film photographed just steps from the president's motorcade. From his perch, what did Abraham Zapruder see?

For 38 years, Dale Myers, a professional computer animator, has researched the assassination. Ten years ago, utilizing new computer technology, he was able to take the 8mm film and analyze it frame by frame, believing it might solve the mystery of whether there was a second shooter in Dealey Plaza.

Dale K. Myers: The Zapruder film was the only film that captured the entire shooting from start to finish. ... Most people don't realize how small the Zapruder film is. An 8mm film is actually smaller than a postage stamp ... and this makes it very difficult to see what's going on, especially when the film is projected in real time. ... I thought there's a way now with the technology to take my computer models and match the Zapruder film exactly, frame for frame ... to finally, once and for all, isolate what's happening in the car as the shots are fired.

Schieffer: To make its lone gunman conclusion work, the Warren Commission maintained that a single bullet hit President Kennedy and then wounded Gov. Connally. Critics dismissed it as a "magic bullet theory." Even Gov. Connally never accepted it.

Gov. John Connally (1992): To me it's just inconceivable that the first shot that went through his neck, entered my back. I don't believe that, I never will believe that. They can't run enough tests to make me believe that.

Myers: Kennedy, when he emerges from behind the sign, he's obviously hit as the hands come up in a very dramatic fashion. So the problem that conspiracy theorists point out is they say, "Well, the time lag between this and the moment when Gov. Connally ... is hit is too short for a single gunman to be firing two rounds." So they say, "This must be a conspiracy." ... Which meant that ... there was a second shooter in the plaza.

The shooting, as we now understand it ... there were three shots fired. ... Zapruder begins filming right here. First shot is fired, bang. Second shot is fired, bang. ... And the third and fatal shot is fired here, bang. ... The reality is, is the president wasn't hit by the first shot. No one was. The first shot missed and Myers' analysis shows what happened with the second shot.

Myers: At frame 222, Connally is not injured. 223, but at 224 ... we can see the right shoulder buckle and start to drop. ... This is a very dramatic change in body position. ... He's clearly been hit. ... We know the bullet has emerged right here in the coat area. And so we can actually see this on camera, the lapel suddenly blow open and then the dramatic reaction of the governor after that. So again, in real time, it's very clear that they both react at the same time.... the two men are ... hit by the same bullet.

This computer technology confirms the controversial single-bullet theory. And by rotating the Zapruder footage in three dimensions, Myers can demonstrate why the single bullet had to pass through Kennedy and hit Connally.

Myers: If you take the entrance wound on Kennedy's back and connect it with a straight line and project that line forward, it hits Gov. Connally, who's seated directly in front of him. It has to hit Connally ... otherwise, you get a real magic bullet, a bullet that exits Kennedy's throat and vanishes into thin air.

But there's more — computer analysis now allows us to investigate the source of the single bullet.

Myers: So we take the back wound on Connally. We take that as a straight line back to Kennedy's throat wound and then just project it ... rearward and see where it takes us. And I was really a little bit surprised after all the conspiracy talk to find it goes right back through the southeastern corner of the Texas School Book Depository.

21st century technology concludes Oswald was the only shooter. And despite all the theories and all the investigations over the last 50 years, no one has yet produced credible evidence of a conspiracy behind Oswald. So why do so many people still refuse to believe a single person did this?

Shenon: It's just — a difficult concept for folks that one young, unstable man with a $21 rifle could change the world. [Pauses] And yet it happened.

A nation united in grief

As rumors and uncertainty spread, one thing was certain: America, and much of the world, was united in unimaginable grief. The president had been assassinated. The drama that was about to unfold in Washington played like an epic tragedy, and television broadcast live images that would be branded into our nation's memory.

Reporter: John Fitzgerald Kennedy, 35th President of the United States, leaving the White House for the last time.

Bob Schieffer: I was always struck by, just what seemed like overwhelming grief that people seemed to be experiencing.

Caro: So the caisson is pulled up to the front of White House. Then they put the coffin on it, put the flag on top of it. Then all of a sudden there she is in the doorway.

Reporter: Mrs. Kennedy, Caroline, and John ...

Caro: Her face is behind the veil. She's holding a little figure in each hand in a sky blue coat — her son and her daughter. She moves forward toward the limousine and Robert Kennedy ... his face is also unforgettable... ravaged face, uh, comes out behind her.

Reporter: President Johnson has gotten into the car with the Kennedy family.

Caro: I mean, here's Lyndon Johnson and Robert Kennedy, two men who hate each other. They're going to be riding behind the body of Robert Kennedy's brother. In this long, slow procession. The caisson pulls away.

Reporter: President John Kennedy ... his body in the casket moving down Pennsylvania Avenue now, up toward Capitol Hill.

Caro: Then they go into the Rotunda.

Schieffer: People felt like they knew the Kennedys. We had seen their family. And so we felt like we were losing someone who was very close to us.

Reporter: The line, 40 blocks long ... estimated by police at 500,000.

Schieffer: There was this one moment where, uh, Caroline reaches up under the flag, to be, obviously trying to be closer to her father. And it wasn't enough just to put her hand on the flag.

Charles Collingwood | CBS News reporting: So great is the crush outside the Capitol, waiting to get in, that people who have not been in line at 10 o'clock can't possibly go by the coffin before it is borne away at 10 o'clock tomorrow.

Reporter: Mrs. Kennedy followed the casket on foot to St. Matthews Church.

Cronkite (1993): It really happened. The president of the United States, dead, and there he lied. It had happened, it was over, it was done, and we were about to bury it. Bury something of our past along with that man.

Schieffer: I think the picture that most people will remember is this tiny little boy, in his little-boy suit, uh, and he puts his hand up... and he salutes. it's hard for me to think of it even today and not be touched by that.

Caro: It's all the pomp and majesty that a republic can muster.

Schieffer: You had the riderless horse.

Caro: The great black horse.

Schieffer: You heard the sound of the drums. ... It was a soft sound. Solid.

Caro: It was like it burned it into our consciousness.

Schieffer: It was overwhelming. ... It was overwhelming.

Caro: When you see these images, even today, you feel this is a watershed moment in American history. ... Really, never to be forgotten.

Schieffer: So many parts of our culture changed because of that weekend. I truly believed it was the weekend that America lost its innocence.

America was never quite the same after that day. A nation that had been brimming with confidence suddenly felt a new vulnerability. How could this have happened? Would it have been different had Kennedy lived? We can never know.

But that weekend was only the beginning of one of the most tumultuous and violent decades in the country's history — a decade that would see more assassinations, Vietnam, bloody riots, and Watergate, which would bring down and force the resignation of a very different president. It would be a time when we would question our leaders our institutions and everything we had taken for granted for so long.

In:
• John F. Kennedy

Bob Schieffer

Bob Schieffer is a CBS News political contributor and former anchor of "Face The Nation," which he moderated for 24 years before retiring in 2015.

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