Authorities are looking for a group of 10 to 15 dirt bike and all-terrain vehicle riders who harassed and assaulted a driver this week on Highway 101 in San Francisco, the California Highway Patrol said.
Cellphone video shot by a witness shows the violent attack as it unfolded about 6:15 p.m. Wednesday near the Cesar Chavez exit, said Officer Vu Williams, a CHP spokesman in San Francisco.
The group of riders had been engaged in an illegal "sideshow" and were performing stunts. Their antics caused traffic to slow a crawl, authorities said.
When the driver of a white Toyota attempted to pass the riders, they boxed him in, Williams said.
The riders then began to ram and punch the man's car.
"These guys don't have a lot of regard for public safety," Williams said. "They got no qualms about even riding on a sidewalk."
When the motorist exited his Toyota to confront the riders, they surrounded him and began to punch and kick him, authorities say.
By the time officers arrived, the dirt bike riders were gone and the injured driver was being loaded into an ambulance.
The victim suffered cuts and a broken leg, Williams said.
Although there is cellphone video of the melee, authorities are having difficulty identifying the attackers. None of the motorcycles bore license plates and the riders wore helmets.
However, Williams said, the group's actions were similar to other "sideshow activity" that officers have seen in the past in the Bay Area.
Anyone with details about the attack is urged to call the CHP's San Francisco office at (415) 557-1094 or the CHP's Golden Gate Communications Center at (415) 551-4100.