Police have confirmed an active shooter at YouTube's headquarters in San Bruno, California. San Bruno police say that police have responded to an address that corresponds with the HQ's address.
Police can be heard describing casualties that are being taken to local hospitals.
No other information about injuries or the possible gunman has been released so far.
People on Twitter described the scene, saying they heard shots fired, police activity and how they were being locked down. Employees say people fled the building in panic after shots were heard.
Vadim Lavrusik, who was working at the headquarters when it started, wrote on Twitter that he was working at his desk when he heard shots and saw people running. He wrote that he had to barricade himself inside a room with other co-workers.