LOS ANGELES (AP) — Nearly a month after counterprotesters attacked a pro-Palestinian encampment at the University of California, Los Angeles, police have made their first arrest, detaining an 18-year-old who is not a student or affiliated with the school in any way, officials said Friday.

UCLA did not identify the suspect, but online county jail records show that 18-year-old Edan On was arrested by UCLA police at 8:46 a.m. Thursday at a business in Beverly Hills and was jailed on $30,000 bail.

Last week, CNN identified On as a high school senior from Beverly Hills who was seen in videos wearing a white mask and white hoodie striking a pro-Palestinian demonstrator with a wooden pole during the April 30 attack on the encampment on campus.

Counterprotesters threw traffic cones, released pepper spray and threw live mice into the encampment, setting off fighting that went on for hours before police stepped in, drawing criticism from Muslim students and political leaders. Police said at least 15 people were injured, though pro-Palestinian supporters put the number closer to 25.

UCLA officials have said the attack involved “a group of instigators.”

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“During that violence, one individual was seen on video assaulting encampment occupants with a wooden pole, causing serious injuries to at least one victim,” the university said in its statement Friday, adding that the suspect was booked at the UCLA Police Department for felony assault with a deadly weapon.

On’s mother wrote in Hebrew in a since-delated Facebook post that “Edan went to bully the Palestinian students in the tents at UCLA” and included an image of the person in the white hoodie that was broadcast on local news, CNN reported. The outlet said his mother confirmed to CNN that the man in the video was her son, though she later said he denies being at UCLA.

Neither On nor his mother could be reached by The Associated Press.

On Thursday, UCLA Chancellor Gene Block, who was among leaders of three universities called to testify at a congressional hearing about the wave of campus protests over Israel’s war with Hamas in Gaza, expressed remorse over the school’s handling of the attack on the encampment.

“Tragically, it took several hours for law enforcement to quell the violence,” Block said. “With the benefit of hindsight, we should have been prepared to immediately remove the encampment if and when the safety of our community was put at risk.”

The night after the attack, hundreds of police officers from various agencies poured onto the campus and dismantled the encampment. On Wednesday, the police chief at UCLA was reassigned “pending an examination of our security processes,” according to a statement from the school.

Protesters tried to establish a new encampment at UCLA on Thursday, but they left when ordered to disperse. A crowd of demonstrators marched elsewhere on campus, and a small group later staged a sit-in inside a building before officers cleared them out.

The arrest followed an investigation that included interviews with victims and witnesses as well as reviews of security camera images and publicly available videos from the public and news media.

The statement said university police are investigating all reported acts of violence associated with protest or counterprotest activities since April 25.