SAN BRUNO, California—It was lunchtime at YouTube headquarters when an employee said there was a noise that “sounded like someone hitting a hammer.”

It was a woman pulling a trigger.

“One of my co-workers faced out the window and yelled, ‘Shooter!’” the employee told The Daily Beast. “And everyone started running in the opposite direction.”

A woman shot three people before killing herself, officials said. Nasim Aghdam of Riverside, California, was reportedly identified as the assailant. Law enforcement officials initially said the incident was under investigation as a domestic dispute, but late Tuesday night officials told the Los Angeles Times and other news organizations that the investigation was looking into a website with Aghdam’s name complaining about YouTube’s policies.

Three people were injured, a spokesperson for San Fransisco General Hospital said: a 36-year-old man is in critical condition, a 32-year-old woman is in serious condition, and a 27-year-old woman is in fair condition.

Zach Vorhies, a senior software engineer, told the Guardian that he “saw a man on the ground with what appeared to be a bullet wound to the stomach.”

Todd Sherman, a product manager for the video-sharing site, tweeted as the incident unfolded: “We were sitting in a meeting and then we heard people running because it was rumbling the floor. First thought was earthquake.”

As he was evacuating the building, Sherman described seeing “blood drips on the floor and stairs.”

People streamed out of the building’s exits and scrambled down a hill into bushes for cover, the employee said. Others ran a block away to the Peninsula Place apartments where assistant manager Claudia Vasquez was standing outside.

“One of the guys yelled, ‘There’s a shooter at YouTube, get inside,’” Vasquez said.

Vasquez said one woman she took in told her she was saved from the gunfire because she fell when the shots started.

The neighborhood surrounding YouTube’s headquarters is normally quiet. A nearby park full of leafy trees and grassy hills would have been tranquil Tuesday if not for the helicopters whirring above and groups of locals and employees huddled in hushed shock, trying to comprehend what just happened.

“The thing about the people at YouTube is that for the most part it’s a bunch of creative, nice people,” an employee told The Daily Beast. “And for somebody to come in and completely destroy that in a sense, that sense of safety and sanctuary, it hits you kind of hard.”

Multiple employees cited YouTube’s policy against speaking to the press as reason they couldn’t give interviews. YouTube told The Daily Beast on Tuesday night: “We have not banned any employees from speaking to the press” after previously declining to answer questions about the policy.

—with additional reporting by Andrew Kirell and Taylor Lorenz