A YouTube video showing a clash between Critical Mass cyclists and a Zipcar driver in San Francisco’s Marina District prompted harsh criticism for the popular cycling movement online as well as from city leaders.

Posted online by someone called Bike42363 on Aug. 29, the video, which has been viewed more than 14,000 times, appears to show the incident that took place Friday at 8:16 p.m.

Although San Francisco police initially told NBC Bay Area they were unable to take any action because nobody had filed a police report, SFPD spokesperson Albie Esparza said late Monday that an investigator would be assigned to the case. "We will reach out to Zipcar to attempt to locate a party involved," Esparza said. "With that being said, we are hoping to speak with both parties involved to obtain a full picture of what happened."

The video starts with a group of Critical Mass cyclists riding with their trademark bright lights and music on Marina Boulevard, shows one of the cyclists riding up to a dark station-wagon and yelling: “Hey, stop that! – No, no, no, no, no no!”

“You ain’t going nowhere,” someone can be heard saying as more cyclists appear in the frame.

“You _______ hit my bike,” the original cyclist can be heard saying, as at least six to seven cyclists surround the car. And then someone yells: “Selfish b_____,” The cyclists keep talking to the driver, who starts backing up after a few minutes. At this point one of the cyclists starts hitting the hood of the car with his bike while another cyclist hits the side of the car with his U-Lock at least three times.

The woman driver finally takes off.

The video prompted San Francisco Supervisor Mark Farrell to release a strong statement against Critical Mass, urging them to respect traffic laws. “Violence is and will never be acceptable here in San Francisco,” Ferrell said, calling the incident disturbing.



“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,” Farrell said. “But, the participants in Critical Mass must understand that actions like this one reflect poorly on the entire group and hurt the group’s overall message and movement.”

Farrell said he was in contact with police to figure out how to prevent similar incidents from taking place in the future.

The Critical Mass Do's and Don'ts posted online tells members not to "pick fights with motorists, even (especially) if they’re itching for one."

“You need to do the right thing and tell the police the identities of your fellow bikers who assaulted this lady!! That is not right! Your group broke all kinds of road laws and then attacked an innocent driver. If you're not going to show this video to law enforcement, then I will,” Bad Drivers Of Napa Valley wrote in the comments section of Bike42363’s YouTube post.

“I don't know the identity of the man who hit the car i've never spoken to him in my life,” Bike42363 responded, He said that the video link had been submitted to the San Francisco Police Department.

Zipcar issued a statement saying they were aware of the incident.

“With any incident of this kind, the well-being of anyone involved is our top concern. As a matter of policy, we’re unable to comment further on any investigation that is ongoing,” spokesperson Lindsay Wester said. “Our company and our members have a long history of supporting bike-related causes, consistent with our mission: to enable simple and responsible urban living. “

NBC Bay Area's Kim Yonenaka contributed to this report.