Officers and federal agents swarmed the company’s complex in the Bay Area city of San Bruno after receiving multiple 911 calls reporting gunfire.
Television news footage showed people leaving the building in a line, holding their arms in the air. Officers patted them down to make sure none had weapons.
YouTube employee Vadim Lavrusik posted on Twitter that he heard gunshots and saw people running. He said he was barricaded in a room with co-workers before being safely evacuated.
Will Hudson said a friend who works for YouTube texted him about the shooter.
“I think there might be a shooter in my building,” read one text. “The fire alarm went off so we started to evacuate and then people (started) running saying there was a shooter.”
San Francisco General Hospital 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, a spokesman said.
The hospital expected more patients.
Google, which owns the world’s biggest online video website, posted on Twitter that the company was coordinating with authorities. The Bureau of Alcohol, Tobacco, Firearms and Explosives said it also responded.
The White House said President Donald Trump was briefed on a shooting and that officials were monitoring developments.
Hudson said his friend made it safely back to San Francisco and was in contact with his family. Hudson said he’s become used to hearing about gun violence but has never been so close to it.
“It just feels strange. It feels like it could really be anyone. That’s really the strangeness of it,” he said.
Calls and emails to YouTube representatives were not immediately returned.