As has become clear, autonomous vehicles are not going to be allowed to proliferate on San Francisco's streets without some kind of protest. And the latest act of protest took things to a newly aggressive level.

A lone, masked, black-clad figure was caught on video Sunday night around 11 p.m., on the 300 block of Buchanan Street in the Lower Haight, taking a hammer to a Cruise vehicle and smashing its censors and windshield before running off.

The disabled car let out a few feeble beeps of its horn, but then remained at the intersection until police arrived.

The act of vandalism was caught on video by Instagram user @caterywta and subsequently reposted by BrokeAss Stuart and Frisco Live 415 on X.

"Officers spoke with a witness, who said that they heard a scream and looked out their window to see the suspect standing in front of the autonomous vehicle. The suspect then began vandalizing the vehicle," said San Francisco Police Sgt. Kathryn Winters, speaking to KRON4.

Cruise hasn't yet commented on the incident, which marks a clear escalation from the mere silliness of putting orange cones on the hoods of robotaxis — something which Cruise and Waymo have already characterized as vandalism, even though it doesn't damage the vehicles like, say, a hammer.

Both Waymo and Cruise received broad approval last month from the California Public Utilities Commission to begin taking paid passengers all around San Francisco at all hours, though neither company is yet broadly doing so. Cruise continues only to operate between 9 p.m. and 5 a.m. and in a specific, (mostly) northern and western swath of the city, and Waymo is similarly keeping its cars out of most of downtown SF, at least with passengers in them. Both companies continue testing cars, with and without people behind the wheel, all over the city.

Shortly following the PUC's approval, Cruise cars were involved in a couple of high-profile incidents, including one in which a female passenger was injured when the vehicle was struck by a speeding fire engine (that it allegedly didn't adequately yield to).

Cruise has also been fighting a PR battle over an August incident report filed by SF firefighters that suggested that a patient in a city ambulance may have died because the ambulance was briefly impeded from leaving a crash scene by two Cruise vehicles blocking a lane.

To date, the only guerrilla protest actions we've seen against these autonomous cars have been claimed by Safe Street Rebel — the group behind the orange-cone actions. There's no indication that this suspect was affiliated with that group.

Manissa Maharawal, an assistant professor at American University who has studied tech protests like this, likened them to the Google bus and Lime scooter protests of earlier years, like the throwing of Lime scooters into the Bay.

"Then there was the burning of Lime scooters in front of a Google bus," Maharawal said, speaking to NPR.

Safe Street Rebel, speaking to the New York Times's Hard Fork podcast month, said that their protests is more a type of street theater meant to raise questions about AVs — like why our streets should be clogged with more cars, as opposed to public transit and bicycles.

Anyone with information about Sunday’s vandalism incident on Buchanan Street is asked to contact the SFPD's tip line at 415-575-4444, or text a tip to TIP411 and begin the message with “SFPD.”

Related: Pranksters Claim They Can Stop Self-Driving Cars With Orange Cones, Waymo and Cruise Not Amused