A man upset with the Discovery Channel's environmental programming took several people hostage at the company's headquarters today, officials said.
Police were negotiating with the gunman, who burst into the suburban Washington building about 1 pm (1700 GMT) wearing what seemed to be metallic canisters strapped to his front and back and waving a handgun.
The gunman had what Montgomery County Police Chief Thomas Manger described as a "small number of hostages" but he did not say how many. He also did not say what the man wants or whether anyone was hurt.
Manger said most of the 1,900 people who work in the building were able to get out safely.
A law enforcement official speaking on condition of anonymity because the investigation is ongoing said authorities have identified James J. Lee as the likely suspect. Police believe he has a handgun but have not confirmed that he has explosives, the official said.
A different official, who spoke on condition of anonymity for the same reason, said Lee previously protested outside the building.
According to a story in The Gazette, which covers Montgomery County, Lee was arrested there in 2008 after throwing thousands of dollars in the air outside the building.
Lee said he planned the protest because Discovery's programming had little to do with saving the planet. He was identified then as being from San Diego, California, although he gave a local address of a homeless shelter.
At the trial, he said he began working to save the planet after being laid off from his job in San Diego. He said he was inspired by "Ishmael," a novel by environmentalist Daniel Quinn and by former Vice President Al Gore's documentary "An Inconvenient Truth."
Adam Dolan, a sales director in Discovery's education division, told The Associated Press by phone that he was heading to lunch with a co-worker when he heard there was a situation in the building.
He was told to go back up to the top floor, lock the door and turn off the lights. Eventually the workers were herded down a stairwell and told to go home.
"Everyone was very scared, but at the same time... I think people were calm and collected and responded as one would expect in this situation," said Dolan, 28.
When he got to the bottom floor, he saw shattered glass near the company's daycare center and suspected it was broken to get the children out. He later got an e-mail that all the children were safe and had been taken to a nearby restaurant.
Another person inside the building told The Associated Press the gunman had something strapped to his chest and had hostages. The person asked not to be identified, saying people inside were told not to speak to the media.
ATF and FBI officials also said they were responding. Authorities descended on the area, and people were being kept away from the main drag of the downtown area where the building is located amid restaurants and shops. Traffic in the area was jammed.
Discovery Communications Inc. operates cable and satellite networks in the US, including The Discovery Channel, TLC and Animal Planet. Discovery shows include "Cash Cab" and "Man vs. Wild," and TLC airs "American Chopper" and "Kate Plus Eight."
Animal Planet also airs the controversial series "Whale Wars," about attempts by environmentalists to disrupt the Japanese whaling industry.