San Francisco police are investigating an incident in which a group of cyclists who were part of a monthly Critical Mass ride last week are seen on video attacking a car and trying to trap a driver who bumped one of their bikes.

The video, posted on YouTube, shows at least a dozen cyclists initially crossing Marina Boulevard in a marked crosswalk Friday night before steering into lanes and toward oncoming, slow-moving traffic.

Police said the cyclists appear to be a “splinter group” of the Critical Mass riders who typically roll through downtown the last Friday of every month.

On the video, one cyclist appears to stop directly in front of a Zipcar, which slowly creeps forward and bumps the bike’s tire.


“Hey stop that!” the cyclist yells before he lays down his bike in front of the car and walks to the driver’s window.

Other cyclists are seen surrounding the car as other vehicles keep their distance.

“You ain’t going nowhere! Put it in park!” someone is heard yelling.

“You’re really going to run me over for stopping for five minutes?” another person is heard saying.


A cyclist, apparently the one whose bike was bumped, is heard telling the female driver that once police arrive on the scene, “you’re done.”

Others yell that she has nowhere to go as about half a dozen cyclists surround her car.

The video shows the driver back up and steer right to go around the group, but they roll in front of her again, trapping her. The driver is heard yelling something to the cyclists about them standing there, then slowly rolls her car forward.

One man lifts his bicycle and slams it on top of her car hood. As the car rolls forward, another cyclist begins smashing the hood with a U-lock. He also hits the driver’s side window and a passenger window as the woman drives off.


San Francisco police spokesman Albie Esparza said that although no one involved in the incident has filed a police report, authorities are investigating anyway because of public interest in the case and the fact that it was caught on video.

The incident took place about 7 p.m. in the Marina district, Esparza said.

Police said the cyclists who hit the woman’s car could be booked for vandalism and cited for traffic infractions for riding into opposite lanes.

The initial contact between the woman’s car and the single bicycle would be investigated as a collision, Esparza said.


“The best thing [they] can do is call police before it escalated,” Esparza said. “One way or another you’re going to have to share the road, no matter what side of the spectrum you’re on.”

“Two wrongs don’t make a right,” Esparza added. “Being surrounded by bicyclists and having them thrown at your car can panic somebody.”

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San Francisco Supervisor Mark Farrell, who represents the Marina district, released a statement Monday regarding the incident:


“Violence is and will never be acceptable here in San Francisco. The actions by the cyclists caught on video this past Friday evening participating in Critical Mass are disturbing and should never be tolerated in our City -- especially the one cyclist seen attacking the vehicle with a bicycle lock repeated times.

“I understand the history that Critical Mass has in San Francisco as a protest movement, and respect that a majority of the participants are peaceful and respectful of others while participating. But, the participants in Critical Mass must understand that actions like the ones this past Friday reflect poorly on the entire group and hurt the group’s overall message and movement.

“I have already been in contact with our police department to evaluate how best to prevent similar future incidents from happening. And, I expect and hope that other Critical Mass participants will condemn the behavior seen this past Friday and actively encourage their participants to respect everyone and all the applicable traffic laws while participating.”

Zipcar issued a statement to local TV station KGO saying it was aware of the incident but had no further comment.


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