A woman shot three people and then turned the gun on herself Tuesday at YouTube headquarters in San Bruno, CA, setting off a chaotic scramble as workers dived for cover, hid in closets and ran from the building, reports the San Francisco Chronicle.

San Bruno police and San Mateo County sheriff’s deputies rushed to the normally quiet office park shortly after the first reports of gunfire came in at 12:48 p.m. and saw dozens of workers running out of the exits.

Inside the building at 901 Cherry Avenue, they came across one victim with a gunshot wound and in an ensuing search of the premises found the shooter with an apparent self-inflicted gunshot wound. Two other victims with gunshots were found at a nearby business, where they had apparently taken refuge, police said.

The three victims were rushed to San Francisco General Hospital. A 27-year-old woman was in fair condition, a 32-year-old woman in serious and a 36-year-old man in critical, authorities said.

Several YouTube employees took to social media to report hearing gunfire and running for their lives. Hundreds of workers were evacuated by police, who made everyone hold their hands up as they filed out onto the street.