A man carrying a hand grenade and shouting threats was shot dead by police Monday in the lobby of the federal courthouse.

The grenade was inactive, but police could not see that as the man held it in his hand, Police Chief Gil Kerlikowske (search) said.

Witnesses said the man, wearing a backpack that he later strapped to his chest, tried to get past security and began shouting threats. Kerlikowske said the backpack contained a cutting board.

The man "often frequented the courthouse as well as the federal building," U.S. Marshal Eric Robertson said, adding he had a "disdain" for the federal government.

The medical examiner's office said it would not identify the man until Tuesday.

In the lobby, a guard saw the man take the grenade out of his backpack, then try to walk across a ledge next to a pool that blocks public access to a secured area, Robertson said.

Judges, jurors, employees and prisoners in the 23-story federal building were evacuated. Meanwhile, security officers tried talking to the man, but he refused to put the grenade down. He also carried a sheaf of papers, including some court documents and what authorities described as a living will.

After about 25 minutes of negotiations with police, "the man made a furtive movement," Robertson said. "At that point the officers had no choice but to stop that threat."

An officer with a .223-caliber rifle and another with a shotgun each fired once at the man, who fell to the floor still holding the grenade.

Bomb squad members determined the grenade had been drilled out and was inactive.

Kim Kingsborough told Northwest Cable News she saw the man in the lobby before he was confronted by authorities. "He just stood around for the longest time in the lobby, looking around," he said.

The man then tried to make his way along the ledge beside the pool, and as officers approached him, Kingsborough said, the man shouted: "Don't come near me!"

Streets around the courthouse, a $171 million high-rise that opened last August, were cordoned off. The building's security features include glass walls that are blast-resistant.