Five members of the Proud Boys street gang — including their leader, Enrique Tarrio — were indicted Monday on seditious conspiracy charges for their role in the attack on the U.S. Capitol on Jan. 6, 2021.

A federal grand jury in Washington, D.C., returned the rare indictment, which charges that Tarrio and four other members of the Proud Boys — Ethan Nordean, Joseph Biggs, Zachary Rehl and Dominic Pezzola — played an outsize role in the planning and execution of the insurrection. A sixth Proud Boy, Charles Donohoe, wasn’t included because he’d already pleaded guilty to conspiracy charges in a plea deal that will force him to testify against his fellow gang members.

Dozens of Proud Boys were among the thousands of people who stormed the U.S. Capitol that day in an effort to stop the certification of Joe Biden as president. Prosecutors say that Tarrio and his fellow defendants were instrumental in the planning stages of the attack; Tarrio allegedly looked over a document titled “1776 Returns” on Dec. 30, 2020, detailing plans to occupy several buildings in Washington on Jan. 6, including six House and Senate office buildings.

Tarrio didn’t join his gang on the day of the insurrection — he was under court order to stay away from D.C. following his arrest over other crimes he committed with the Proud Boys in December — but the other members led the charge. They stood at the front of a massive throng that marched to the Capitol following a speech by defeated President Donald Trump, joined by members of the Oath Keepers, a self-described “militia” that often shows up to Proud Boys events, whose leaders are also facing seditious conspiracy charges.

Several people died as a result of the attack on the Capitol, including police officers, and hundreds more were injured.

Seditious conspiracy is serious and rarely prosecuted. It holds that two or more people not only conspired to carry out an attack, but did so with an intention to “overthrow, put down, or to destroy by force the Government of the United States.”

The seditious conspiracy charges will be slapped on top of the conspiracy charges each member already faced. They’re scheduled to appear together in court on June 9.

The indictment comes the same week that a House committee tasked with investigating the events of Jan. 6 is prepared to hold its first hearings.

Andy Campbell is the author of forthcoming book “We Are Proud Boys: How A Right-Wing Street Gang Ushered In A New Era Of American Extremism,” coming to bookstores on Oct. 4, 2022.

This article originally appeared on HuffPost and has been updated.