Washington —  A federal contractor working for the FBI has been arrested after allegedly stealing an FBI vehicle from bureau headquarters Tuesday afternoon. 

Later, a handgun magazine belonging to the agent who drove the car was found inside the vehicle, charging documents filed Wednesday revealed.

John Worrell, of Virginia, worked for an outside government contracting agency and was assigned to FBI headquarters, prosecutors said, when he allegedly stole the dark green four-door Ford sedan from an FBI garage and drove to another FBI facility in Vienna, Virginia. There, investigators say Worrell displayed the credentials of the federal agent to whom the car was assigned and tried to gain entry to the facility. 

Worrell isn't an FBI agent or a law enforcement officer, but he was authorized to be at the bureau's headquarters in Washington, D.C., because of his work as a contractor. 

He "claimed to have a classified meeting at the Vienna FBI facility," but did not have the necessary access cards, prompting officials to deny him entry there, according to court documents. Worrell allegedly tried to enter the Vienna facility a second time and after again being denied, he spent about 45 minutes in the parking area. 

Worrell later provided his real identification to security officials at the Vienna facility, who called the police. 

Prosecutors alleged that during a consensual search of the FBI-issued vehicle by police, officers uncovered a "loaded handgun magazine" from a fanny pack inside the car that belonged to the unnamed agent who drives the car. Court documents indicated Worrell wasn't aware that the magazine was inside, since he told officers he was not aware of any weapons in the car. 

During an interview, Worrell told investigators he "believed he had been receiving coded messages, which appeared in various forms including e-mails, 'stage whispering,' and a variety of different context clues over the course of several weeks, indicating that [he] was in danger, and thus he was attempting to go to a secure facility where he could be 'safe,'" according to charging documents. 

Investigators said in court documents that limited parking at the FBI headquarters requires keys to be left inside cars parked in its garage "to allow vehicles to be moved by authorized personnel on an as-needed basis." The unnamed agent's credentials were also inside. 

After discovering the vehicle was missing at 1:15 p.m. on Tuesday, the FBI agent searched the garage and alerted security at 2:22 p.m., nearly two hours after security camera footage viewed after the incident showed the car leaving headquarters. 

During his interview with investigators, Worrell admitted that he did not have permission to use the car, according to court documents. It is unclear if he is still employed by the unnamed government contracting agency. 

Last year, an FBI agent was carjacked in a Washington, D.C., neighborhood after two individuals held the agent at gunpoint amid a surge of car thefts in the nation's capital. The vehicle was found less than an hour later, about a mile from the site of the theft. 

An attorney for Worrell could not be immediately identified. Worrell is being held pending a detention hearing on Friday.

The FBI declined to comment on this report and referred CBS News to court records. 

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Robert Legare

Robert Legare is a CBS News multiplatform reporter and producer covering the Justice Department, federal courts and investigations. He was previously an associate producer for the "CBS Evening News with Norah O'Donnell."