Federal prosecutors on Friday accused Philadelphia Proud Boys president Zach Rehl of conspiring with three other leaders of the militant far-right group in leading a mob that overwhelmed police during the Jan. 6 Capitol attack in an attempt to stop certification of the 2020 election results.

A six-count indictment, unsealed in federal court in Washington, offered a detailed glimpse of encrypted communications between more than 60 members of the organization before, during, and after the ransacking of the building. The charges constitute the most significant allegations to date against the upper echelon of any of the organized groups believed to have participated.

According to the filing, Rehl — a former Marine who was raised in a family of Philadelphia cops — celebrated as the nation reeled from the insurrection that left more than 130 police injured and one officer dead.

“I’m proud as f— [of] what we accomplished yesterday,” he allegedly wrote on social media.

Investigators have described the Proud Boys, whose members are among former President Donald Trump’s most vocal and violent supporters, as one of the primary instigating forces behind the attack and have charged 20 of its members so far — more than any other organized group. And Rehl, who was arrested Wednesday at his home in Port Richmond, has emerged as one of its most visible members on the East Coast.

» READ MORE: Pennsylvania man charged with assaulting Officer Brian Sicknick with bear spray during Jan. 6 Capitol riot

He and the three others charged Friday — Ethan Nordean, 30, of Auburn, Wash., Joe Biggs, 37, of Ormond Beach, Fla., and Charles Donohoe, 33, of Keenersville, N.C. — face charges including conspiracy, obstruction of Congress, and destruction of government property. The most serious counts could send them to prison for up to 20 years. Prosecutors said they will seek to hold Rehl in custody until trial at a detention hearing scheduled for Tuesday.

The indictment accuses all four men of plotting what unfolded Jan. 6 for weeks if not months. But the conspiracy case, as laid out in Friday’s filing, could face some of the same challenges that have arisen in similar prosecutions of members of the Oath Keepers, another right-wing group.

Defense lawyers in those cases have argued that while the government has produced plenty of evidence suggesting their clients organized trips to Washington, they have not yet substantiated claims that they arrived with a plan to commit violence or breach the Capitol’s security perimeter.

Prosecutors, in the filing Friday, accused the Proud Boys leaders of using websites to fund-raise and programmable radios and encrypted apps to coordinate their movements.

But while many of the communications they quoted contained threatening language and talk of how to evade the detection of law enforcement or counterprotesters as they marched through Washington, none directly referenced a plan to storm the Capitol that day.

“We tried playing nice and by the rules,” Nordean, a self-described Proud Boys sergeant-at-arms who also goes by the name Ruffio Panman, wrote on social media in the weeks before the attack. “Good luck to all you traitors of this country we so deeply love ... you’re going to need it.”

Proud Boys national chairman Enrique Tarrio — who was not in Washington on the 6th but who, according to the indictment, was briefed in advance on the group’s planning — has maintained they had no intention at the outset to enter the Capitol or interrupt Congress.

Rehl’s attorney, Shaka M. Johnson, declined to directly respond to the allegations, saying he had not yet had a chance to review the indictment. Still, he defended his client’s character as a veteran, homeowner, and expectant father of a child due this summer, and signaled his intent to challenge the charges in court.

“He’s a standup person,” Johnson said. “He has given of himself to this country. There are allegations that have been made. While he rebuffs them, he understands this is the process.”

The indictment put Rehl at the core of an organized Proud Boys assault.

“Hopefully the firing squads are for the traitors that are trying to steal the election from the American people,” he posted on social media in late November.

Roughly a month later, Tarrio called on social media for members to “turn out in record numbers” for the Save America rally planned in Washington on Jan. 6. He warned them to dress “incognito” and spread out in smaller groups to avoid scrutiny. Rehl told the others he was bringing specially-programmed radios that are more difficult to monitor or overhear, prosecutors said.

But Tarrio was arrested Jan. 4 on charges related to a previous, violent pro-Trump protest in the city, sending the Proud Boys plans briefly into chaos.

Donohoe worried their communications might now be compromised.

“Listen to me real good!” he wrote to the others on the encrypted chat app the day of Tarrio’s arrest, according to the indictment. “Everything is compromised and we can be looking at Gang charges. Stop everything immediately! This comes from the top!”

New chat channels were created specifically for Jan. 6 — including one named “Boots on the Ground” — to coordinate the movement of members. According to the indictment, they met at the Washington Monument at 10 a.m. and took off on a winding march before Trump had even taken the stage at the rally playing out near the White House.

Photos and videos that have circulated widely on social media show Nordean, Biggs, and Rehl — wearing a camouflage “Make America Great Again” cap and carrying a Temple Owls backpack — leading a crowd of roughly 100 Proud Boys members along the way.

» READ MORE: Philly Proud Boys president Zach Rehl marched alongside leaders charged in Capitol riot

When they arrived at the Capitol’s west side to find security barriers already toppled by others in the crowd, they quickly forced their way to the front of the attacking mob, the charging documents say.

“We’ve just taken the Capitol,” Biggs allegedly announced on a video. He was among the first people to enter the Capitol building after another Proud Boys member, charged separately, smashed through windows with a stolen police riot shield, prosecutors said.

Rehl did not enter the building until more than an hour later, according to the indictment, which offered no details on what he did once inside.

A photo published in a January edition of the New Yorker magazine captured him smoking a cigarette and checking his cell phone in a mob of rioters carousing in the office of Sen. Jeff Merkley (D., Ore.).

That image was not referenced in Friday’s court filing. Instead, the filing focused on what Rehl and his codefendants did after.

Donohoe purportedly messaged the others to organize a second assault on the building later that afternoon. Nordean and Biggs boasted of their participation on social media. And Rehl, prosecutors said, was already making plans for the future.

“We need to start planning,” he allegedly wrote the day after the attack. “We are starting planning for a Biden presidency.”

Read the indictment: