Prince William County Police block the street near the house where the FBI made an arrest, in Woodbridge, Va., Thursday. (AP Photo/Steve Helber)

WASHINGTON (AP) — 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 attack, an abrupt breakthrough in an investigation that for years flummoxed law enforcement and spawned conspiracy theories about Jan. 6, 2021.

The arrest marks the first time investigators have publicly identified a suspect in an act that has been an enduring mystery for nearly five years in the shadow of the violent Capitol insurrection.

The suspect was identified as Brian J. Cole Jr., 30, of Woodbridge, Virginia, 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 following day by supporters of President Donald Trump.

Law enforcement officials used credit purchases of bomb-making materials, cellphone tower data and a license plate reader to zero in on Cole, according to an FBI affidavit filed in the case. The FBI and Justice Department declined to elaborate on what led them to the suspect, but characterized his arrest as the result of a reinvigorated investigation and a fresh analysis of already collected evidence and data.

“Let me be clear: There was no new tip. There was no new witness. Just good, diligent police work and prosecutorial work,” Attorney General Pam Bondi said at a news conference.

Calls to relatives of Cole listed in public records were not immediately returned Thursday. Hours after Cole was taken into custody, unmarked law enforcement vehicles lined the cul-de-sac where Cole’s home is while FBI agents helped shoo away onlookers. Authorities were seen entering the house and examining the trunk of a car nearby.

The pipe bombs were placed on the evening of Jan. 5, 2021, near the offices of the Democratic and Republican national committees. Nobody was hurt before the bombs were rendered safe, but the FBI has said both devices could have been lethal.

In the years since, investigators have sought the public’s help in identifying a shadowy subject seen on surveillance camera even as they struggled to determine answers to basic questions, including the person’s gender and motive and whether the act had a clear connection to the riot at the Capitol a day later, when supporters of Trump stormed the building in a bid to halt the certification of the Republican’s 2020 election loss to Democrat Joe Biden.

Seeking a breakthrough, the FBI last January publicized additional information about the investigation, including an estimate that the suspect was about 5 feet, 7 inches tall, as well as previously unreleased video of the suspect placing one of the bombs.

The bureau had for years struggled to pinpoint a suspect despite hundreds of tips, a review of tens of thousands of video files and a significant number of interviews.

Investigative clues

An FBI affidavit filed in connection with Cole’s arrest lays out a series of circumstantial clues that investigators pieced together.

Using information from his bank account and credit cards, authorities discovered he purchased materials in 2019 and 2020 consistent with those used to make the pipe bombs, according to court papers. That included galvanized pipes and white kitchen-style timers, according to the affidavit. The purchases continued even after the devices were placed.

Cole owns a 2017 Nissan Sentra with a Virginia license plate, the affidavit says. Around 7:10 p.m. on Jan. 5, 2021, Cole’s vehicle drove past a license plate reader less than a half mile from where the person who placed the devices was first spotted on foot around 7:34 p.m. that night, the document says.

In the absence of harder evidence, Republican lawmakers and right-wing media outlets promoted conspiracy theories about the pipe bombs. House Republicans also criticized security lapses, questioning how law enforcement failed to detect the bombs for 17 hours. Dan Bongino, the current FBI deputy director, floated the possibility last year — before being tapped for his job — that the act was an “inside job” and involved a “massive cover-up.”

The FBI’s top two leaders, Bongino and Director Kash Patel, sought to breathe new life into the investigation despite having openly disparaged the bureau’s broader approach to the Jan. 6 siege and despite Trump’s pardons on his first day back in office of the rioters who stormed the Capitol, including those who violently attacked police with poles and other makeshift weapons.