City Manager Connie Jackson says there have been multiple 911 calls reporting a shooting and that police and fire officials have responded. The city has responded with a "massive police and fire".
In the audio, you hear an officer note there's a woman down with a gunshot wound to her chest.
San Bruno City Manager Connie Jackson told NBC Bay Area that there is no immediate danger to the public.
Authorities didn't disclose their conditions.
YouTube's headquarters houses almost 2,000 employees.
According to a report by KRON4, an active shooter has been reported at YouTube headquarters in San Bruno, California.
"We heard the shots first, and that immediately drew us over to the window to see what the heck's going on, and next thing you know, you see people streaming out just running, dozens of them, just running out the front exit", Marco Tartaglia said.
Sports Apparel maker Under Armour says data breach affected 150 million users
Credit card data was not breached either, the company said, because payment information is collected and processed separately. Under Armour also doesn't collect any government information, like Social Security numbers or driver's license information.
"We were all suddenly aware of a lot of noises, of sounds, people running outside of the room where she was".
There is security at all the buildings, the employee told CNN.
" 'I have to get out of here, ' " the woman said the colleague said. People at the fast-food restaurant tried to use napkins to stop the bleeding.
One Twitter user posted an image of what appears to be people outside of the YouTube building with their hands up.
Local media footage showed those leaving the building being patted down by police officers. Several roadways near the building were closed to traffic.
More videos regarding the YouTube shooting can be viewed on Twitter. In 2006 Google said it was purchasing YouTube for $1.65 billion in stock.
Zuckerberg General Hospital told NBC News that it had received three patients and was expecting more, while Stanford Medical Center said it was expecting four or five patients.