Three police officers at the Fruitvale BART station early on New Year's Day have a young black man, Oscar Grant, pinned on the ground, and one of them shot him in the back and murdered him. (Grant and a group of other people were being held and questioned regarding reports of a fight on the train. He was not armed.)
Video report from local news station KTVU here. News account from San Francisco Chronicle here (and the video seems to fully corroborate the worst version of the story from witnesses in the written account).