A gunman police shot to death after he took hostages at Discovery Channel's headquarters said he hated the company's shows such as "Kate Plus 8" because they promote population growth and its environmental programming because it did little to save the planet.

Three hostages — two Discovery Communications employees and a security guard — escaped unhurt after the four-hour standoff Wednesday in Silver Spring, just outside the nation's capital. After several hours negotiating with the gunman, tactical officers moved in when authorities monitoring him on building security cameras saw him pull out a handgun and point it at a hostage, Montgomery County Police Chief Thomas Manger said.

Capt. Paul Starks, a county police spokesman, identified James J. Lee on Thursday as the suspect.

Manger said and officer shot and killed Lee after hostages began moving and police heard a "pop" they believed to be either a gunshot or an explosive device detonating.

Lee repeatedly said he was "ready to die," according to Manger.

It wasn't the first time Lee, a homeless former Californian, had targeted Discovery's headquarters. In February 2008, he was charged with disorderly conduct for staging a "Save the Planet Protest." In court and online, he had demanded an end to Discovery Communications LLC's shows such as TLC's "Kate Plus 8" and "19 Kids and Counting."

Instead, he said, the network should air "programs encouraging human sterilization and infertility."

"Humans are the most destructive, filthy, pollutive creatures around and are wrecking what's left of the planet with their false morals and breeding cultures," Lee wrote in a bitter manifesto on his website.

Lee, 43, also objected to Discovery's environmental programming. He wrote in 2008 that a show he called "Planet Green" was "about more PRODUCTS to make MONEY, not actual solutions."

Police say the gunman burst into the building about 1 p.m. and took hostages in the lobby on the first floor. A gun wasn't his only weapon, as an explosive device on his body detonated when police shot him, Manger said. Authorities later sent in a robot to disarm a device on the gunman's body.

Manger told CBS News on Thursday that the hostages were very courageous. He said the gunman "repeatedly said that he was ready to die." Manger said the hostages "had to be terrified."

Starks said Thursday that the gunman had four crude explosive devices strapped to him. He described two of them as green propane cylinders with pipes attached that contained shotgun shells. The other two were pipe bombs. He said Lee also had what appeared to be a remote radio frequency or a remote switch with an antenna on it. Starks said that had officers concerned that Lee could use remote control to set off bombs. Police also discovered batteries, two handguns and two ski masks at the scene.

The building was to reopen briefly Thursday for employees to return, although the lobby remained closed as police investigate. Counselors were offering assistance to Discovery Channel employees, said Catherine Frymark a company spokeswoman.

NBC News reported that after its producers called Discovery's general number, a man identifying himself as Lee got on the phone and said he had a gun and several bombs.

"I have several bombs strapped to my body ready to go off. I have a device that if I drop it, if I drop it, it will ... explode," the man told NBC.

He said he built the bombs in about three weeks. "I did a lot of research. I had to experiment," he said.

One hostage, Discovery employee Jim McNulty, posted a message on the company's website, thanking authorities for "helping to ensure the safety of all my colleagues" and "for helping to get me and my fellow hostages out safely." He said he wouldn't talk now about what happened because police were still investigating.

Starks said the suspect had shot a gun at least once and that authorities believe he was acting alone but are investigating all possibilities.

Lee's mission against the Discovery Channel goes back at least a few years.

In the February 2008 protest in which he was arrested, he threw fistfuls of cash in the air and paid homeless people to carry signs condemning the network. Police found his pockets stuffed with more than $20,000, according to court records.

Lee served two weeks in jail after his arrest during which doctors evaluated his competency to stand trial. County State's Attorney John McCarthy said Lee was ordered to stay 500 feet away from Discovery headquarters as part of his probation, which ended two weeks ago.

Lee faulted the Discovery Channel for shows as varied as "Future Weapons," ''It Takes a Thief" and "Planet Green." Instead, he sought programming based on "My Ishmael," a book by philosopher Daniel Quinn in which a telepathic gorilla instructs a 12-year-old girl on society's failings. On his MySpace page, Lee said his heroes were Quinn and "Star Trek" commander James T. Kirk.

Quinn said in an interview from his Houston home that Lee misinterpreted his book's message about the folly of continually increasing food production to meet population demands.

The author said he hadn't heard of Lee before Wednesday but called his death "pretty horrible." Had he been able to speak with him, he would have told Lee "he's giving a bad name to the ideas that he's trying to espouse."

Lee in 2008 also held a related contest promising $200,000 worth of Hawaiian real estate for the best essay proposing a save-the-planet TV show. On his MySpace page that has since been taken down, he lists his home as Hawaii.

The Maui News and KHON-TV reported that Lee had lived in the Lahaina area of West Maui. The newspaper reported that he was a 1985 graduate of Lahainaluna High School and his former classmates and principal described him as a normal person who didn't cause any trouble.

"As far as I'm concerned, he was a good kid," former Lahainaluna principal Henry Ariyoshi told The Maui News.

None of the 1,900 people who work in the building were hurt, and most made it out before the standoff ended Wednesday.

"We're relieved that it ended without any harm to our employees," said David Leavy, Discovery's executive vice president for corporate affairs.