Arrest Made in Martin Luther King Day 'WMD' Plot

March 9, 2011 — -- An arrest has been made in the failed January bomb plot that apparently targeted marchers along an Martin Luther King Day parade route in Spokane, Wash.

Kevin William Harpham has been charged with illegal possession of an explosive device and attempting to use a "weapon of mass destruction," according to charging documents released today.

Investigators are looking into possible ties between Harpham and white supremacist groups, an FBI official told ABC News. The Southern Poverty Law Center, which tracks hate groups, reported that in 2004 Harpham was a member of the Neo-Nazi group National Alliance.

Additionally, a house in the Spokane suburb of Addy, Wash., is being searched by police, according to a report by ABC News' Spokane, Washington affiliate KXLY.

The bomb was discovered by three workers just half an hour before Spokane's MLK Day parade was set to begin on Jan. 17, the FBI said.

Authorities rerouted the parade while officers from the Spokane Police Department's bomb disposal unit worked on the bomb.

U.S. Attorney General Eric Holder confirmed the arrest had been made and said today the bomb "was planted with the aim of injuring or killing people."

"We were fortunate that it did not go off and people were, in fact, not killed. We were just lucky in that regard," he said in a press conference.

Frank Harrill, the FBI supervisory senior resident agent in Spokane, told ABC News during the initial investigation that the backpack was "a viable device."

"The potential for lethality was clear," he said.

According to an FBI press release, "Subsequent preliminary analysis revealed the backpack contained a potentially deadly destructive device, likely capable of inflicting multiple casualties."

If convicted, Harpham could face life in prison, according to the Eastern District of Washington U.S. Attorney Michael Ormsby.

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