Six months after the Capitol Hill insurrection, the Justice Department is still hunting for scores of rioters which reflects the massive scale of investigation and the grueling work.

The first of more than 500 people already arrested have pleaded guilty.

Among those who still haven’t been caught: the person who planted two pipe bombs outside the offices of the Republican and Democratic national committees the night before the melee, as well as many people accused of attacks on law enforcement officers or violence and threats against journalists.

The FBI website seeking information about those involved in the Capitol violence includes more than 900 pictures of roughly 300 people labeled “unidentified.”

Authorities made a few arrests on 6 January and were engaged in clearing the building and moving lawmakers to safety.

The FBI has since received countless tips and pieces of digital media from the public. But a tip is only the first step of a painstaking process. And authorities have no record of many of the attackers because this was their first run-in with the law.

“Most of these people never showed up on the radar screen before,” said Frank Montoya Jr., a retired FBI special agent who led the bureau’s field offices in Seattle and Honolulu. It’s not like what happens in movies, he added.

John Scott-Railton is a senior researcher at the Citizen Lab at the University of Toronto who has been collaborating with journalists and others to identify suspects using digital clues. He said that while much is known about the “small fish” who committed crimes that day, a deeper understanding is needed of the actions of organized group leaders.

“We all need to be in a place where we can have conversations about what Jan. 6th was that go beyond a bunch of individuals motivated by a set of ideologies who showed up at the Capitol,” he said.

Those being sought include many accused of violent attacks on officers. One video released by the FBI shows an unidentified man attacking officers with a baton. In another, a man is seen ripping the gas mask off an officer who screamed in pain as he was being crushed into a doorway by the angry mob.

In some cases, social media platforms have turned over incriminating posts that defendants tried to delete after their gleeful celebrations of the siege gave way to fears of being arrested. Often, the attackers’ own family, friends or acquaintances tipped off authorities.

In one case, the FBI used facial comparison software to find a suspect on his girlfriend’s Instagram account. Agents then went undercover, secretly recorded the man at work and got him on tape admitting to being in the crowd, which he described as “fun.”

“The more of these people you identify – potentially through search warrants and social media communications – you’re going to be able to identify others,” said Tom O’Connor, who focused on counterterrorism as a special agent before leaving the bureau in 2019. “Those people who have been arrested will then be given the opportunity to cooperate and identify other persons involved.”

The FBI has offered a reward of up to $100,000 for information leading to the arrest of the person responsible for planting the pipe bombs in Washington on 5 January.

Footage shows a person in a gray hooded sweatshirt, a mask and gloves appearing to place one of the explosives under a bench outside the Democratic National Committee and the person walking in an alley near the Republican National Committee before the bomb was placed there.

It remains unclear whether the bombs were related to planning for the insurrection.

Justice Department officials say arresting everyone involved in the insurrection remains a top priority.

“They will find them,” said Robert Anderson Jr., former executive assistant director of the FBI’s Criminal, Cyber, Response, and Services Branch. “I don’t care how long it takes. If they are looking for them, they will find them.”

The only defendant who has been sentenced is an Indiana woman who pleaded guilty to a misdemeanor and was spared any time behind bars.