Montgomery County Police confirm with EW that an armed man entered the Discovery Channel headquarters — located in Silver Spring, Md. — and is holding at least one person hostage. According to police, calls were made at approximately 1 p.m. about a man with a gun, and possibly explosives. The area has since been cleared out. Police, bomb technicians, and a SWAT team are on the scene, attempting to contact the man, who is located in the lobby.

The Associated Press reports that a person inside the building claims the man “had something strapped to his chest,” and is also holding explosives. The person also told the AP that those inside the building have been ordered to not speak to media.Other witnesses have claimed to have heard shots fired in the building.

UPDATE: According to NBC News, authorities have identified the gunman as James J. Lee, someone who is believed to have had “concerns” with the Discovery Channel, and has protested at the building in the past. He is believed to have taken “a small number of hostages,” and is speaking with police. At this point, police have not confirmed whether or not Lee has explosives on his person. Lee had been previously arrested at the site before; back in 2008, he was taken into custody after the threw thousands of dollars in the air nearby the building.