Federal investigators are looking at race as a possible motive in the attempted bombing of a Martin Luther King Day parade in Spokane, Wash., as they hunt "armed and dangerous" suspects.
"I think the connection is virtually inescapable... that the device was planted and left there to target the marchers or bystanders," Frank Harrill, special agent in charge of the FBI's Spokane office, said late Tuesday.
According to the Southern Poverty Law Center, 15 different "hate groups" operate in Washington state and six others just over the border in Idaho -- including the white supremacist group Aryan Nations. The FBI said the men or women responsible are being considered "armed and dangerous."
Whatever the motive, Spokane mayor Mary Verner said the attempted bombing was "unacceptable."
"I was struck that on a day when we celebrate Dr. King, a champion of non-violence, we were faced with a significant violent threat," Verner said Tuesday. "This is unacceptable in our community, or any community."
Just half an hour before the Martin Luther King Day parade was scheduled to begin Monday, three workers spotted a suspicious package with visible wires on a bench, the FBI said.
Authorities rerouted the parade while officers from the Spokane Police Department's bomb disposal unit worked on the bomb.
"I saw the robot and when I saw the robot I told my girls to run and 'Let's get out of here,'" witness Lisa Ludeman told ABC News.
Harrill, the supervisory senior resident agent in Spokane, told ABC News that the backpack was "a viable device."
"The potential for lethality was clear," Harrill said Tuesday. The local bomb squad neutralized the device, he added.
FBI: Bomb Was 'Likely Capable of Inflicting Multiple Casualties'
According to an FBI press release, "Subsequent preliminary analysis revealed the backpack contained a potentially deadly destructive device, likely capable of inflicting multiple casualties."
The bomb, described as a small pipe bomb, was designed to be triggered by a radio frequency system, and was directional -- meaning it was designed to spray its deadly shrapnel in the direction it was pointed, law enforcement sources said. Aimed at the parade route, it could have caused multiple casualties among the marchers. About 1,500 people showed up for the parade.
The case is being actively investigated by the FBI's Inland Northwest Joint Terrorism Task Force, and the FBI is offering a $20,000 reward for information leading to the arrest and conviction of whoever made the device.
The FBI has released pictures of the bag and two tee-shirts that were in the bag. The FBI is attempting to locate local security camera footage and is also asking individuals who have pictures or video from the event to contact the FBI.