Terrified employees trying to avoid being targets during yesterday’s mass shooting at YouTube headquarters in San Bruno relayed their experiences and feelings through Twitter.

The shooter was reportedly 39-year-old Nasim Aghdam, a San Diego resident who police say may have been angry at the company for what she perceived as a “suppression” of her online videos. After shooting three people, Aghdam apparently turned the gun on herself. According to news reports, the three gunshot victims are listed in critical, serious and fair condition at San Francisco General Hospital. A fourth employee injured their ankle while fleeing the scene. Police say there is no evidence that Aghdam knew her victims.

One employee tweeted that there was an active shooter at the facility. “Heard shots and saw people running while at my desk. Now barricaded inside a room with coworkers.”

One worker reported mistaking the sound of people running for an earthquake. Another said he saw “blood drips” on the stairs.

“At that point every new person I saw was a potential shooter,” tweeted one.

All of the approximately 1,100 employees who work at the facility in the heart of Silicon Valley were evacuated from the building. Some ran into the woods or to a nearby shopping center for shelter.

Chris Dale, head of communications at YouTube, described the company as  “an incredibly tight-knit community.” He added: “It feels like the entire community of YouTube and all employees were victims of this crime.”