The FBI has arrested a 30-year-old Virginia man and charged him with planting a pair of pipe bombs in Washington the night before the January 6, 2021, assault on the US Capitol by supporters of President Donald Trump.
The suspect, Brian Cole Jr., of Woodbridge, was charged with use of an explosive device and attempted malicious destruction by means of explosive materials, Attorney-General Pam Bondi and other federal officials told a Washington press conference.
Bondi and other officials did not say what motivated the alleged bomber to plant devices outside the Republican and Democratic Party buildings near the Capitol, or reveal what new break in the case led to the arrest nearly five years after the incident.
"This investigation is ongoing. As we speak, search warrants are being executed, and there could be more charges to come," Bondi said on Thursday, noting that a deep review of existing evidence led investigators to Cole.
Police deactivated the bombs the day Trump supporters stormed Congress in an attempt to stop lawmakers from certifying Democrat Joe Biden's 2020 presidential election victory. Thousands of rioters stormed the Capitol that day, assaulting about 140 officers and causing more than $US2.8 million ($A4.2 million) in damage.
It was unclear if Cole had a lawyer. He lives with his parents in Woodbridge, a suburb about 30km outside Washington, and works for a bail bond company, according to a court filing, which capped a lengthy investigation in which the FBI had long struggled to identify a suspect.
Cole purchased components used in the bombs in 2019 and 2020, including pipes, kitchen timers and battery connectors, according to an FBI affidavit laying out the evidence in the case.
Trump pardoned nearly everyone criminally charged for participating in the riot, some 1500 people, when he returned to office in January.
The pipe bomb probe was one of a few cases that had drawn significant attention from Trump's political base, which the FBI's top two officials, Kash Patel and Dan Bongino, vowed to re-examine.
Patel told the press conference that officials "brought in a new team of investigators and experts, re-examined every piece of evidence, sifted through all the data".
In January, prior to Trump taking office, the FBI released new surveillance video to reinvigorate the investigation that had already offered a $US500,000 ($A760,000) reward and received more than 600 tips at the time.
