A New York City judge’s son who stormed the U.S. Capitol wearing a furry “caveman” costume was sentenced on Friday to eight months in prison.

U.S. District Judge James Boasberg told Aaron Mostofsky that he was “literally on the front lines” of the mob’s attack on Jan. 6, 2021.

“What you and others did on that day imposed an indelible stain on how our nation is perceived, both at home and abroad, and that can’t be undone,” the judge told Mostofsky, 35.

Boasberg also sentenced Mostofsky to one year of supervised release and ordered him to perform 200 hours of community service and pay $2,000 in restitution.

Mostofsky had asked the judge for mercy, saying he was ashamed of his “contribution to the chaos of that day.” “I feel sorry for the officers that had to deal with that chaos,” said Mostofsky, who must report to prison on or after June 5.

Federal sentencing guidelines in his case recommended a prison sentence ranging from 10 months to 16 months. Prosecutors recommended a sentence of 15 months in prison followed by three years of supervised release.