A police riot shield used to break a window, then a door kicked open from the inside — new court documents detail the first moments of the Jan. 6 breach of the U.S. Capitol that left five people dead and more than 100 police officers injured.

A criminal complaint against two Montana brothers and a detention memo against a prominent member of the Proud Boys help explain how, the government believes, one segment of a mob overran a small, poorly defended line of Capitol Police officers. In these and other filings, prosecutors trace the actions of possible key instigators in the storming of the Capitol, including members of the Proud Boys — a far-right nationalist and nativist group with a history of violence — and other right-wing extremist groups.

According to prosecutors, citing surveillance video and social media, Proud Boy Dominic Pezzola was one of the first to lead the charge both outside and inside the Capitol, helping overwhelm police defenses after stealing an officer’s riot shield.

Starting at about 1 p.m., Pezzola, known as “Spaz,” was among the first protesters to charge and overwhelm a line of police behind a pedestrian gate on the west-front Capitol grounds, prosecutors said. The crowd advanced toward a second set of waist-high metal barricades at the Capitol’s west plaza, where Pezzola and another Proud Boy dragged a piece of the fence away, leaving police unprotected and helping thousands follow onto the Capitol grounds, prosecutors said. Pezzola next was among the first to reach another police line at the base of the Capitol, prosecutors said.

As a scuffle broke out after a member of the mob was hit by a projectile, possibly fired by police, Pezzola can be seen on video pulling out a riot shield, according to prosecutors. He is then seen in images using the shield to break a building window at 2:13 p.m., according to court documents.

“Pezzola was not the only person trying to break windows and forcibly enter the Capitol at that time, but he appears . . . first to breach a window so successfully that he and other rioters could enter the Capitol through it,” Assistant U.S. Attorney Erik Kenerson wrote. “The defendant’s actions show planning, determination, and coordination.”

Late Friday, a federal grand jury returned a new indictment adding a conspiracy charge against Pezzola, 43, of Rochester, N.Y., and another man previously charged in the riot, William Pepe, 31, of Beacon, N.Y., also an alleged member of the Proud Boys, who was identified in his charging papers as wearing an American flag bandanna. Prosecutors said the men conspired to obstruct and impede police protecting the Capitol, including by removing metal barricades meant to hold back crowds.

Prosecutors say two brothers from Montana, Joshua Calvin Hughes and Jerod Wade Hughes, followed Pezzola into the window and then helped kick down a door from the inside, giving more rioters access.

The Hughes brothers were charged late Thursday with felonies related to destruction of property, obstructing law enforcement and disrupting a government proceeding. They could not be immediately reached for comment.

Pezzola faces similar charges. The indictment Friday added counts alleging that he assaulted police and stole the riot shield, two additional crimes of violence.

“I’ve been provided the government’s memorandum and will be filing a responsive memorandum prior to the detention hearing Monday,” his attorney Michael Scibetta said. He added that D.C. jail officials had denied Pezzola contact with both his attorney and a pretrial services worker assigned to prepare a report recommending whether Pezzola should be detained, saying he was in “protective custody.”

“Wouldn’t he be better served being released, to be safer and afforded a meaningful legal defense?” Scibetta said. “The jail wouldn’t even confirm that he was held there when I called.”

According to prosecutors, members of the Proud Boys used walkie-talkie-style communication devices to coordinate during the attack. On Pezzola’s computer, Kenerson said, FBI agents found information on making homemade firearms, poisons and explosives. Once inside the Capitol, authorities say, Pezzola and the Hughes brothers engaged in a confrontation with Capitol Police Officer Eugene Goodman at the foot of a staircase, according to an FBI agent’s affidavit, “advancing . . . in a menacing manner.” While Doug Jensen, 41, of Des Moines is identified as the “primary aggressor,” the Hughes brothers “followed immediately” behind him, the agent wrote. Pezzola, according to prosecutors, was also part of the group.

Standing beside Pezzola in a confrontation with officers inside the Capitol was Robert Gieswein, 24, a Colorado paramilitary trainer and alleged member of the anti-government Three Percenters right-wing group, according to prosecutors, who have charged Gieswein. He was also recorded multiple times inside and outside the Capitol in military gear, moving with Proud Boys, prosecutors alleged.

Jensen, a self-described believer in the Q-Anon extremist ideology, was arrested the weekend after the riot.

Goodman lured the rioters away from the Senate chamber by lightly pushing Jensen, a tactical maneuver that experts say preempted a violent confrontation and may have saved lives. He has since been made acting deputy sergeant-at-arms, and he escorted Vice President Harris on Inauguration Day.

Internal and congressional investigations are examining the failure to fend off the rioters, who forced lawmakers to hide in corners of the building as the angry mob called for their deaths. In the court filings, authorities say police were outnumbered by rioters at every turn. While Goodman called for backup and was joined by other officers in an upstairs atrium, the FBI said they still lacked the manpower to attempt any arrests.

“So instead they used their training to try and de-escalate the situation by talking with individuals in an attempt to calm them down,” an agent wrote in an affidavit. The crowd refused, shouting, “This is our house,” “This is our America,” and “We’re here for the corrupt government.”

When one rioter slammed a fire extinguisher on the floor, sending up a cloud of smoke, the agent said, the shock helped quell the crowd’s anger, and it dispersed. But the Hughes brothers did not leave the building, prosecutors say, and made their way onto the Senate floor, where they sat in lawmakers’ chairs and rifled through their desks.

Meanwhile, Kenerson wrote, Pezzola filmed himself smoking a “victory cigar” in another part of the building. Prosecutors alleged that Pezzola said in the video: “Victory smoke in the Capitol, boys. . . . I knew we could take this mother­f---er over [if we] just tried hard enough.”