UPDATED 5:35 PM ET
Montgomery County police officials have 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 have identified the man as James J. 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.
David Leavy, Discovery's executive VP of communications and corporate affairs, said in a statement late Wednesday that the company was "relieved and grateful" that employees and the children at the day care center were unharmed. "Employees in Silver Spring demonstrated courage, compassion and cooperation throughout the situation, which aided law enforcement efforts -- for which we are thankful and proud," he said.
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."
In a rambling manifesto, Lee inveighs against "disgusting human babies" and "parasitic infants" and calls on Discovery to "broadcast to the world their commitment to save the planet."
A 2008 post on the site attributed to someone named "Lee" rails against Discovery.
"These guys have been very sneaky and deceptive as to their contribution to the planetary problems. Just look at their ‘new' show about saving the planet, "Planet Green," to me, it's just another show about more PRODUCTS to make MONEY, not about actual solutions. We can't let them get away with doing it anymore. Join me in the PROTEST AGAINST THE DISCOVERY NETWORK to get them to start broadcasting real shows that actually work to save the planet. But not just a show about THEM TELLING US WHAT LIGHTBULB TO USE, but shows where solutions are brought to the new shows from people all over with good ideas."
As the crisis was initially unfolding, employees inside the building were in contact with media organizations. Ari Fischer, a project manager at Discovery, told ABCNews.com that the gunman had taken a security guard and several other employees hostage.
"We couldn't see the weapon. We peered in and could make out his silhouette," Fischer told ABCNews.com. "We saw him holding a security guard at his side. There were other people on the floor, a dozen or so."
"Friends, I am in a work closet with workers here. There is a shooter here at Discovery. I am ok," read a text from another Discovery employee.