At least four people were injured, one of them critically, in a shooting at YouTube’s headquarters in San Bruno, Calif., on Tuesday afternoon, the police said. The shooter, who the police said was a woman, died from an apparently self-inflicted gunshot wound.

Brent Andrew, a spokesman for San Francisco General Hospital, said at a news conference that the hospital had received three patients: a 36-year-old man in critical condition, a 32-year-old woman in serious condition and a 27-year-old woman in fair condition. The condition of the fourth victim, and what hospital he or she was at, was not clear.