Montgomery County police officials confirmed that the gunman who had entered the Discovery Communications headquarters in Silver Spring, MD Wednesday has been shot and killed.
Three hostages, a security guard and two other employees, are safe, said officials. And police bomb disposal units have begun to sweep the building for additional explosives.
News reports from the scene say that there was "a pop" and the canisters on the suspects back began to smoke.
Multiple news outlets identified the man as James Jay Lee. He is well-known to local authorities as a radical environmentalist who has allegedly organized multiple protests outside Discovery headquarters for what he believes is the network's dearth of programming about environmental dangers including global warming and over-population.
Live news reports earlier in the day showed employees being evacuated from the building, which also houses a day care center.
An early report from the Associated Press said that Lee had what appeared to be canisters, possibly containing explosives, strapped to his chest and back. Police had brought in hostage negotiators and asked people who may have still been inside the building not to contact the media.
A Montgomery County police spokesman confirmed that the gunman appeared to have "some sort of explosive device." The spokesperson said they had "an unconfirmed report" of shots fired. He also said that police had surrounded the building.
During a brief press conference at about 3:20 p.m. ET, Montgomery County authorities would not confirm that the gunman was indeed Lee. A police spokesman said "most" of Discovery's 1,900 employees were out of the building and that the gunman was on the first floor with an unconfirmed but small number of hostages.
Discovery representatives did not immediately respond to a request for comment.
Speaking on MSNBC, NBC News justice correspondent Pete Williams said Lee had been arrested in 2008 for a protest during which he tossed large amounts of cash into the air. Footage of that scene were replayed on WJLA, the ABC in Silver Spring. The video showed a throng of people scrambling after the cash. Lee was charged with disorderly conduct and littering, which resulted in six months probation and a $500 fine. According to WJLA, Lee represented himself in that case and was apparently evaluated by a psychiatrist. On his MySpace page, Lee explained that he began his environmental crusade after being laid off from his job in San Diego. His local address in Silver Spring turned out to be a homeless shelter.
Lee is reportedly the founder of Save the Planet Protest, which according its web site, aims to "save what's left of the non-human Wildlife by decreasing Human population."