Documentary filmmaker Nick Quested followed the Proud Boys through Washington as members of the extremist group marched on the Capitol on Jan. 6 and clashed with police officers.
His firsthand, searing account of the riot will be a central piece of the House Jan. 6 select committee's prime-time hearing Thursday night, which will feature both his testimony and some of the never-before-seen footage of the Proud Boys and other rioters he turned over to investigators.
ABC News has exclusively obtained some of that extraordinary material, showing how a group of Trump supporters at a presidential rally transformed into an angry mob that broke into the Capitol to try to overturn the 2020 presidential election.
"I am not allowed to say what's going to happen today because everyone's just gonna have to watch for themselves. But it's gonna happen," one woman in the crowd told Quested ominously. "Something's gonna happen one way or another."
Quested's material shows some of the most infamous Capitol rioters in the hours before they appeared in the halls of Congress, including Jacob Chansley, the "QAnon Shaman" later sentenced to more than three years in prison for his role in the attack.
"Freedom!' Chansley shouts, with his horned fur hat and spear on the National Mall.
Quested captured the moment just before 1 p.m. when protesters overpowered Capitol Police officers at the outer perimeter of the complex, turning over a series of bicycle racks and rushing closer to the Capitol building.
Inside the swarming crowd at the base of the Capitol, he witnessed police officers frantically pushing rioters backwards as their perimeter crumpled, and Trump supporters swinging from scaffolding, using flags as weapons and crowd surfing closer to the violence at the Capitol's west entrance.
A member of Quested's film crew also followed the rioters into the halls of Congress, where some marched around the House chamber looking for House Speaker Nancy Pelosi, D-Calif., chanting, "All we want is Pelosi!" and "Nancy!"
The speaker was evacuated by her Capitol Police detail minutes before rioters marched through her office. Some of her youngest staffers locked themselves in empty rooms and sheltered under tables.
Quested himself was assaulted during the riot, as a protestor tried to grab and smash his camera.
The committee on Thursday will also hear testimony from Capitol Police officer Caroline Edwards, who was one of the first officers injured during the riot when she was thrown to the ground by rioters pushing bike racks forward and hit her head on the concrete stairs.
They also plan to feature clips of taped interviews with Trump administration officials and family members, including Jared Kushner and Ivanka Trump.
The committee expects to use videos, social media posts and pictures throughout the public hearings planned for June and has retained former ABC News president James Goldston to help produce the upcoming sessions.
Along with Quested's footage, the committee has also obtained 14,000 hours of security camera video from Capitol Police.
A spokesman for the committee declined to comment.