The Verge reports that a person jumped on the bonnet of the car and smashed its windscreen, before a crowd surrounded the vehicle and sprayed it with paint, broke its windows, and threw fireworks inside.
The fire brigade arrived minutes later, but the car was already a flaming wreck. Waymo spokeswoman Sandy Karp told The Verge that the car was empty when it was targeted.
The arson comes amid rising tensions between locals and robot car operators. Just last week, a Waymo car hit a cyclist who was behind a lorry turning across its path.
A video on YouTube shows the burnt-out shell of the electric Waymo Jaguar. Another video by software developer Michael Vendi shows the scene as the fire raged.
It is unclear if this is just louts being loutish or an anti-robo car protest. San Francisco's 49ers play in the Super Bowl this afternoon, so last night's festivities for Chinese New Year could be followed by more mayhem tonight. Police Chief Bill Scott has begged residents to behave. "Please don't light anything on fire" so it might be a San Francisco thing.