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Federal agents have arrested the son of a New York City judge on charges that he was among the protesters who stormed the U.S. Capitol, the FBI said Tuesday.

Aaron Mostofsky was picked up at his brother’s home in Brooklyn on Tuesday morning, about a week after he was seen inside the Capitol wearing a fur costume and a police vest he is accused of stealing during the mayhem.

Following a teleconference hearing, a judge freed Mostofsky on $100,000 bail but banned him from traveling Washington except for purposes related to his case there, the Associated Press reported.

Court papers show how investigators are combing through internet communications to identify alleged offenders like Mostofsky, who referred to himself as a “caveman” eager to protest the presidential election results.

Mostofsky, 34, was to make a remote court appearance later in the day to face charges including felony theft of government property — a police bulletproof vest worth $1,905 and a riot shield valued at $265.

Mostofsky’s unusual garb made him stand out from the crowd of camouflage-wearing, flag-waving marauders. At one point, he was photographed sitting on a bench near the Senate chamber holding a stick and the riot shield, which he said he picked up off the floor.

He also gave a video interview inside the building, telling the New York Post he was there “to express my opinion as a free American that this election was stolen.”

Before the protest, Mostofsky messaged another demonstrator that he could be found by looking for “a caveman,” adding, “Even a caveman knows it was stolen,” the court papers said. Afterward, as his photo circulated, he said the image was unfortunate because “now people actually know me,” they add.

Mostofsky’s father is Steven Mostofsky, a state court judge in Brooklyn. He has not responded to requests for comment made through court administrators.

Messages seeking comment were left for Aaron Mostofsky’s brother, Nachman, and his defense attorney.

Nachman Mostofsky is the executive director of Chovevei Zion, the The Jewish Heritage Preservation Society, and vice president of the South Brooklyn Conservative Club.

He told Gothamist last week that his brother “did nothing illegal,” “was not part of the riot” and was only in the Capitol because he was “pushed inside.”