Police chief Ed Barberini of San Bruno city, 19 km from San Francisco, said the suspect, a female shooter, appeared to have shot herself after injuring multiple people at the campus of the YouTube facility on Tuesday, Xinhua news agency reported.
"We did locate a victim with what we believe to be a self-inflicted gunshot wound," said Barberini. "It's a female, but the investigation is still ongoing before we can put all the pieces together."
The shooting reportedly took place in an outdoor cafe at the YouTube campus, which houses at least 1700 employees. Search for other shooters inside the building is on.
The four injured people have been taken to Zuckerberg San Francisco General Hospital. A 32-year-old female and a male (36) are reported to be in serious condition, while another female victim aged 27 is in a fair condition. .
Todd Sherman , a YouTube employee and a witness described the entire series of events in his tweets.
He said: "We were sitting in a meeting and then we heard people running because it was rumbling the floor. First thought was earthquake."
"After exiting the room we still didn’t know what was going on but more people were running. Seemed serious and not like a drill. We headed towards the exit and then saw more people and someone said that there was a person with a gun." He said in his further tweets.
"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. I looked down and saw blood drips on the floor and stairs. Peaked around for threats and then we headed downstairs and out the front. "
"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."
Google, the parent company of YouTube, issued a statement earlier, saying that "We continue to actively coordinate with local authorities and hospitals. Our security team has been working closely with authorities to evacuate the buildings and ensure the safety of employees in the area."
YouTube CEO Susan Wojcicki tweeted: "There are no words to describe how horrible it was to have an active shooter @YouTube today. Our deepest gratitude to law enforcement & first responders for their rapid response. Our hearts go out to all those injured & impacted today. We will come together to heal as a family."
US President Donald Trump tweeted that he had been briefed on the shooting at the YouTube headquarters.
"Was just briefed on the shooting at YouTube's HQ in San Bruno, California. Our thoughts and prayers are with everybody involved," he tweted.