Hundreds of judges, jurors, employees and prisoners in the 23-story building were evacuated and surrounding streets were cordoned off Monday as dozens of police cars responded, jamming lunchtime traffic.
Officers could not tell that "what appeared to be a World War II-type of grenade" was inert until after the shooting, Police Chief Gil Kerlikowske said.
The man, dressed in camouflage, was identified in newspaper and television reports as Perry Manley, 52, of Seattle. FBI agents and other authorities would not confirm the identification.
The man had frequented the courthouse as well as the federal office building and often expressed "a disdain for the federal government as well as some of its policies," U.S. Marshal Eric Robertson said.
"I believe it's more of a global government frustration," Robertson said.
Susan Calhoun, Manley's former wife, told KING Television he became embittered and quit a high-paying job after their divorce in 1990 when a judge ordered him to make support payments for their three children. The children are now grown and those payments were no longer required, KING reported.
According to the report, Manley also had e-mailed the station recently, criticizing the child support system and claiming that millions of noncustodial parents were being illegally impoverished by the government.
Police and federal agents searched a Belltown apartment building Monday evening. FBI agent Roberta A. Burroughs would not comment on news reports describing it as Manley's residence.
Five years ago, the Seattle Post-Intelligencer reported, Manley paraded down a Bremerton street waving a flag and wearing little more than a sandwich board that read, "State Raped."
Manley came under investigation in April by the FBI after U.S. District Judge Thomas S. Zilly denied his attempts to bring a state lawsuit to the federal level. Cases brought by Manley also were rejected two years ago and in 2001.
In a letter filed in court in April, Manley accused Zilly of treason, adding that such a crime was punishable by death. Subsequently, on a fathers' rights Web site, he wrote that he was visited by two federal agents.
On Monday, the suspect arrived at the courthouse shortly before noon with a backpack that he later strapped to his chest. Witnesses said he tried to skirt security in the lobby and began shouting threats, police Detective Christie-Lynne Bonner said.
The backpack contained unspecified court documents and a living will, indicating he might have expected police to shoot him, as well as a cutting board which the man may have intended to use as a protective device, Kerlikowske said.
Security officers were unable to talk the man into putting down the grenade, police were called and after about 25 minutes of negotiations "the man made a furtive movement," Robertson said. "At that point the officers had no choice but to stop that threat."
Chay Adams, 27, of Seattle, said she witnessed the shooting while after leaving the U.S. Marshals Service office on the ninth floor where her father is a deputy marshal.
She and about eight other women were evacuated to the fifth floor, from which she saw police confront the man, who had been sitting on a bench with a yellow backpack strapped to his chest in the ground floor atrium lobby.
He was nervous and kept clasping his hands, but there was nothing unusual about him, she said. "If they wouldn't have known what happened, you wouldn't have paid any attention to him," Adams said.