The shocking events at the headquarters of one of the world's biggest technology names YouTube quickly emerged on social media.
Employees of the firm live-tweeted their rush to escape from the campus in San Bruno California.
Comments and footage were posted to Snapchat, Twitter and Instagram, showing workers streaming out of the building and armed police going in.
Within minutes of news breaking, Todd Sherman, a Product Manager at the video giant, posted an account of his escape on Twitter.
We were sitting in a meeting and then we heard people running because it was rumbling the floor. First thought was earthquake. https://t.co/gmolQmRXm1— Todd Sherman (@tdd) April 3, 2018
After existing the room we still didn’t know what was going on but more people were running. Seemed serious and not like a drill.— Todd Sherman (@tdd) April 3, 2018
Then Mr Sherman said he and his colleagues headed towards the exit and someone told them there was a person with a gun.
At that point every new person I saw was a potential shooter. Someone else said that the person shot out the back doors and then shot themselves.— Todd Sherman (@tdd) April 3, 2018
He then looked down and saw blood on the floor. He looked around for potential threats and headed down the stairs and out of the front of the building.
Police cruisers pull up, hopped out with rifles ready and I told them where the situation was as I headed down the street to meet up with a couple team members.— Todd Sherman (@tdd) April 3, 2018
In an Uber omw home. Hope everyone is safe.— Todd Sherman (@tdd) April 3, 2018
Another employee, Vadim Lavrusik, said he was initially barricaded with colleagues, then escaped.
Active shooter at YouTube HQ. Heard shots and saw people running while at my desk. Now barricaded inside a room with coworkers.— Vadim Lavrusik (@Lavrusik) April 3, 2018
Safe. Got evacuated it. Outside now.— Vadim Lavrusik (@Lavrusik) April 3, 2018
If you’re a friend in news, I know you are doing your job and appreciate you reaching out to check if I’m okay but the last thing I want to do is an interview right now. We are all shakin up.— Vadim Lavrusik (@Lavrusik) April 3, 2018
Other YouTube workers hurriedly used their social media accounts to tell people they were safe.
Active shooter at YouTube HQ. Most of us are in lockdown or have been evacuated. We don’t know much right now.— Jonathan Willing (@willing) April 3, 2018
People who knew those inside posted screenshots of WhatsApp and text conversations with panicked colleagues.
Posts tagged into the location on Snapchat showed police responding at the scene, and evacuating employees.
Users who work close to the YouTube HQ said that they had also been put under lockdown.
Gunshots at the @youtube office in San Bruno. My office across the street is on lockdown.— Miles⁶𓅓 (@KXCMiles) April 3, 2018
Others nearby posted images of the scene and emergency response.
Student activists from the Parkland shooting used social media to share their solidarity with the video sharing company.