UPDATE: San Bruno Police Chief Ed Barberini has confirmed four people were transported to local hospitals with injuries while the body of a woman, believed to be the shooter, was found inside the building with self-inflicted gunshot wounds.
Earlier: Police in California are responding to an active shooter situation at the YouTube headquarters in San Bruno.
Dozens of officers and SWAT teams surrounded the well known building at 901 Cherry Avenue after employees reported hearing gunfire, injuries are unknown at this stage.
Many workers tweeted about the situation while still inside the building including Vadim Lavrusik, who was one of the first to post about it on social media.
"Active shooter at YouTube HQ. Heard shots and saw people running while at my desk. Now barricaded inside a room with coworkers," he posted.
While product manager Todd Sherman, reported seeing blood drops on the floor and stairs.
"We were sitting in a meeting and then we heard people running because it was rumbling the floor. First thought it was an earthquake," he said.
Media footage from the scene shows dozens of workers being led out of the building with their hands about their heads, as police crews rushed into the offices.
While Google, YouTube's parent company released a statement, saying they are "coordinating with authorities and will provide official information here from Google and YouTube as it becomes available."