San Francisco police officers arrested 20 people late Saturday night in SoMa after breaking up an unauthorized “Stud Alley” block party with hundreds of participants, according to the police department. It marked the second round of arrests of Pride attendees this weekend after police arrested five people at the tail end of the Trans March on Friday. 

Police officers arrived near Kissling and 11th streets at 10:58 p.m. and “encountered an unsanctioned and unpermitted block party” that had about 300 participants and a D.J., according to a statement from the San Francisco Police Department. The following details are based on the department statement and social media videos; two participants reached by Mission Local declined to comment. 

The department said that the large crowd “prompted the response of additional SFPD resources.” Social media footage shows dozens of officers marching through SoMa streets armed with batons, wearing riot helmets and carrying plastic zip-ties.

Officers then gave an order to disperse, the department said, and told the D.J. to leave the area. The D.J. left but the partygoers did not, the department said, and officers tried to “disperse the crowd.” Two people “resisted,” the department said, and officers arrested them.

Several people also “vandalized two vehicles passing through the area,” the department said, and made them “inoperable.” The two vehicles may have been Waymos: One online video shows two Waymos in the street blinking hazard lights, and appears to show one officer telling others that the Waymos had been vandalized. 

The party then reformed a few blocks later at Washburn Street about two blocks away, the department said, with about 200 people; the police shut that gathering down as well.

Footage from the scene shows a line of officers in tactical gear advancing rapidly on the crowd, shoving people out of the alleyway before forming a cordon line to block the street. In total, 18 people were arrested on Washburn Street, the department said, for “obstructing or delaying a peace officer and unlawful assembly.” 

The department said that “makeshift barricades” had been set up to keep officers at bay; at one point in a video, an officer moves several large rocks that were placed in the street. Two officers sustained minor injuries, the department said.

SoMa has been the site of unsanctioned “Stud Alley” parties on the Saturday evenings of Pride weekend for at least the past six years. The parties have made headlines in past years for graffiti, broken windshields and outraged neighbors. 

The organizers of Stud Alley posted an announcement this year that they would not host a party, saying that the party had recently “outgrown itself,” but reminded past party-goers of the unofficial slogan that is frequently graffitied onto walls around the party: Every alley is Stud Alley. 

Jesse, a bartender at the nearby bar the Willow, reported seeing cops “everywhere” after the Saturday incident, when people “fled” to the bar to escape. He did not report hearing of any incidents of violence between party-goers and police. 

The arrests mark the second encounter between Pride-goers and police this weekend. On Friday, at the end of the Trans March, police officers arrested five marchers for alleged vandalism and assault after march-goers allegedly spray-painted several statues and a person.

On Sunday afternoon, Washburn and Kissling streets still bore signs of the party. Spray painted on the walls of buildings were “Fuck SFPD,” “No Cops at Pride,” and “Every Alley Stud Alley.”