SEATTLE (Reuters) – The FBI is treating the investigation of an unexploded backpack bomb left along the parade route of a Martin Luther King Jr. holiday celebration as a possible case of domestic terrorism, an agency spokesman said on Tuesday.
The unattended Swiss Army-brand backpack, with wires visible, was discovered Monday morning on a downtown bench by three city workers who notified police of the device about 30 minutes before the parade was scheduled to begin, the FBI said.
The parade, attended by about 1,500 people, was quickly rerouted while city's bomb disposal unit was summoned and safely "neutralized the device," the FBI said.

Bomb found along Martin Luther King Jr parade route - Yahoo! News