The bomb that exploded outside Spokane City Hall was significantly different from two pipe bombs detonated exactly four weeks earlier in the Valley, authorities say.
A timer and electronic ignition apparently detonated Monday’s bomb, suggesting a more sophisticated device, sources said.
Someone lit fuses to ignite the galvanized metal pipe bombs that blew up on April 1 at The Spokesman-Review’s Valley office and a branch of U.S. Bank.
“It’s definitely a different construction than we saw in the Valley,” one investigator said.
A damaged clock and bits of a paper sack were among the pieces of evidence meticulously gathered outside City Hall, sources said.
While the bomb was described generally as a pipe bomb, sources said the housing was something other than galvanized pipe.
Investigators believe the bomb may have been concealed in a paper sack and placed against the east doors of City Hall.
Bomb fragments are being analyzed by Bureau of Alcohol, Tobacco and Firearms experts who can nearly reconstruct such devices.
The City Hall bombmakers packed the pipe with shrapnel - potentially lethal nails and screws. No notes were left behind.
In the Valley blasts, the bombers used galvanized pipe secured with end caps. The bank bomb was powerful enough to blow one of the end caps through two walls.
The Valley bombs contained no nails or screws.
At the newspaper office and the bank, the bombers left behind a two-page note suggesting possible ties to radical Aryan militants known as the Phineas Priesthood. No arrests have been made. The FBI says the robbery and bombings could be the work of as many as five suspects.
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