The man, Matthew Greene, of Syracuse, New York, admitted to plotting with other members of the far-right group to stop Congress from certifying Joe Biden as the winner of the 2020 presidential election. As part of his plea, Greene, an Army National Guard veteran, agreed to cooperate with prosecutors.
He is the first member of the extremist group, which describes itself as a "pro-Western fraternal organization for men who refuse to apologize for creating the modern world," to plead guilty and cooperate in a Jan. 6-related case.
Prosecutors said in court filings that Greene joined the Central New York Proud Boys chapter in December 2020 and that he and other members planned and coordinated their activities for and on Jan. 6 ahead of time, including using programmable radios.
The group met at the Washington Monument and marched together to the Capitol complex, where Greene "was one of the first people who traversed past toppled police barricades," prosecutors said.
"He was at the front of the line of rioters when police started using crowd-control measures, which included pepper spray," court filings say, but he appears to have retreated and never made it into the Capitol building itself.
He later boasted about his actions using encrypted messaging apps, telling an acquaintance, "we took the capital," the filings say. He also told another Proud Boys member in the days after the attack that they needed to be prepared to "do uncomfortable things."
A search of his home in January turned up four unregistered guns, including an AR-15, according to court documents.
Greene is scheduled to be sentenced March 10. Under federal sentencing guidelines, he is likely to face over four years in prison, but prosecutors could ask for less time depending on his level of cooperation.
Federal authorities have identified more than three dozen people charged in the Capitol siege as Proud Boys leaders, members or associates, including at least 16 defendants who are charged with conspiracy.