More than three weeks after counterprotesters attacked a pro-Palestinian encampment at the University of California, Los Angeles, the university police have made the first arrest related to the attack: an 18-year-old who officers said had beaten pro-Palestinian protesters with a wooden pole.
The U.C.L.A. police did not identify the man by name, but arrest records show that he is Edan On. He is facing one charge of felony assault with a deadly weapon. The police said he inflicted serious injuries on at least one person.
In videos of the April 30 attack on the encampment, a man in a light-colored hoodie and a white mask is seen swinging a pole at several protesters. In one photograph, there appears to be blood on the sleeve of his sweatshirt.
Mr. On’s mother told CNN that the man seen in those videos was her son, though she later told the network that he had denied being there. She told CNN last week that her son was a high school senior with plans to join the Israeli military.
Mr. On was arrested on Thursday morning at a business in Beverly Hills, the police said. Jail records show that bail was set at $30,000.
Mr. On’s mother and father declined to comment on Friday.
The U.C.L.A. Police Department has been under intense pressure to identify and charge counterprotesters involved in the April 30 attack, which the police allowed to continue for several hours without intervening.
The university created a new office of campus safety, temporarily removed its police chief from his post and hired an outside police consultant to review its response to the attack.
The new leader of the campus safety office, Rick Braziel, said in a statement on Friday that the university police were committed to identifying more of the perpetrators of the attack. “Those who inflicted violence on our community will be held accountable to the fullest extent of the law,” he said.
The attack occurred several days after students formed the encampment, part of a wave of student protests against Israel’s invasion and bombing of Gaza. On the night of April 30, a group of counterprotesters — some of whom wore pro-Israel slogans on their clothes and played Israel’s national anthem — arrived and began trying to dismantle the encampment. They dragged barricades away from the camp, punched and kicked protesters and launched fireworks into the crowd.
It was not until about 3 a.m. on May 1 that police officers in riot gear intervened to separate the two groups. No one was arrested at that time.
The next night, U.C.L.A. called in officers from the city police force to assist in clearing the encampment. More than 200 pro-Palestinian protesters who refused to leave were arrested.
U.C.L.A.’s chancellor, Gene Block, testified before a congressional committee on Thursday about how he had handled the student protests on campus. During that hearing, he faced intense questioning from Representative Ilhan Omar, Democrat of Minnesota, who asked him why none of the counterprotesters involved in the April 30 attack had been arrested.
“Are any of these people in jail?” she asked.
Jail records indicate that Mr. On was arrested during Dr. Block’s testimony, but his arrest was not publicly disclosed until Friday.
Jonathan Wolfe contributed reporting from Los Angeles. Alain Delaquérière contributed research.
