0342 GMT August 23, 2019
Police in San Bruno, south of San Francisco, converged on YouTube's headquarters after receiving numerous reports of a shooting.
A female suspect has died of a self-inflicted gunshot wound, police have said.
San Bruno police chief Ed Barberini said three people had been taken to hospital with gunshot wounds.
A 36-year-old man was in critical condition, a 32-year-old woman was in serious condition and a 27-year-old woman was in fair condition, a spokesman for San Francisco General Hospital said.
Local television images showed YouTube employees walking out of the building with their hands raised.
Staff inside the building reported hearing gunshots. Some barricaded themselves in before being evacuated.