WASHINGTON -- The FBI on Thursday arrested a man accused of placing two pipe bombs outside the headquarters of the Republican and Democratic national parties in Washington on the eve of the U.S. Capitol riot, an abrupt breakthrough in an investigation that for years flummoxed law enforcement and spawned conspiracy theories about Jan. 6, 2021.

The suspect was identified as Brian J. Cole Jr., 30, of Woodbridge, Va., but key questions remain unanswered after his arrest on explosives charges, including a possible motive and what connection if any the act had to the assault on the Capitol the next day by supporters of President Donald Trump.

Law enforcement officials reviewed credit card purchases of pipe bomb components, cellphone tower data and a license plate reader to zero in on Cole, acc

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