It happened while the Mayor London Breed's car was parked in Japantown.
Mayor Breed is out of town, so Supervisor Vallie Brown was using it in her role as Acting Mayor.
"She's not going to let me use it anymore is she?" Brown half-joked. "It's back to bicycling for me... I have to wait until mom comes home."
The driver's side mirror will have to be replaced.
There is no word on what happened to the driver.