Derek Nelson, a former U.S. Marine and Conan O'Brien lookalike, wore goggles and a respirator as rioters tried to breach the House floor during Capitol attack, the feds say.

An alleged Jan. 6 participant who online sleuths dubbed “Conan O’Riot” due to his resemblance to former late-night talk show host Conan O’Brien was arrested by the FBI this week.

Derek Nelson, who was an active-duty U.S. Marine from October 2011 to September 2015, was arrested in Champaign, Illinois, on Wednesday, according to federal court records. Along with his co-defendant, Derek Dodder of Nevada, 30-year-old Nelson faces four misdemeanor charges in connection with the U.S. Capitol attack.

Online “Sedition Hunters” dubbed the redheaded Nelson #ConanORiot, using the hashtag to track his movements at the Capitol. The sleuths had identified Nelson more than two years ago, by the summer of 2021.

Nelson was dressed up in colonial attire on Jan. 6, specifically “a brown tricorn hat along with a blue double-breasted button coat and red or maroon undershirt with a white scarf around his neck,” according to the FBI. In one video cited by the FBI, filmed near the Washington Monument, where crowds had gathered to watch then-President Donald Trump’s speech, a videographer asks Nelson why he’s there.

“To start a revolution,” Nelson said. "Why are you here?”

When the crowd descended on the Capitol, Nelson was near the front lines as a pro-Trump mob chased down outnumbered officers on the west side of the building, according to the FBI.

Once inside the Capitol, Nelson wore goggles and a respirator mask, and video presented as evidence in another Jan. 6 case shows him running away after another rioter sets off a fire extinguisher near the doors to the House of Representatives, which were barricaded as members fled the violent mob.