A retired firefighter who threw a fire extinguisher at police officers during the U.S. Capitol riot was sentenced on Tuesday to more than four years in prison.

Robert Sanford struck two police officers in the head with the fire extinguisher that he threw as he stormed the Capitol on Jan. 6, 2021, with a mob of Donald Trump supporters. He also threw an orange traffic cone at a Capitol police sergeant.

“Sanford also hurled obscenities and insults at the law enforcement officers on the Lower West Terrace, calling them ‘traitors,’” a prosecutor, Janani Iyengar, wrote in a court filing.

One of the officers struck by the fire extinguisher had a bump and swelling on his head; the other had a headache and went to a hospital for a medical exam, prosecutors said.

U.S. District Judge Paul Friedman sentenced Sanford to four years and four months in prison followed by three years of supervised release, according to an online court record. Federal prosecutors had recommended a prison sentence of five years and 11 months.

Sanford, 57, of Boothwyn, Pa., worked as a firefighter for 26 years before retiring in 2020. A fire extinguisher is “an instrument that he was uniquely familiar with and should have known how much damage it could cause,” the prosecutor wrote.

Sanford traveled to Washington, D.C., with friends from Pennsylvania on bus trip organized by the conservative activist group Turning Point USA. He listened to speeches at Trump's “Stop the Steal” rally before joining the crowd that marched over to the Capitol and disrupted the joint session of Congress for certifying Democrat Joe Biden's electoral victory over Trump.

Sanford was arrested on Jan. 14, 2021. He has been jailed since he pleaded guilty last September to assaulting, resisting or impeding police officers using a dangerous weapon — a felony punishable by a maximum of 20 years in prison.

Sanford began to work with a specialist in cult deprogramming in August 2022 and was confronted with “facts” about the baseless conspiracy theory that Democrats stole the 2020 presidential election from Trump, according to defense attorney Andrew Stewart.

“Even after he was incarcerated, he participated in regular discussions designed to challenge his ideology and belief structure, then help him understand how and why he developed the beliefs that led him to make the decisions that he did on January 6,” Stewart wrote in a court filing.

Sanford believed that police had attacked him and others without provocation when he picked up and threw what felt like an empty fire extinguisher, his lawyer said.

“Certainly, this is not a justification for his action nor is it intended to be,” Stewart wrote.

More than 1,000 people have been charged with federal crimes related to the Jan. 6 riot. Over 600 of them have pleaded guilty or been convicted after trials decided by a jury or judge. Over 450 of them have been sentenced, with over half getting terms of imprisonment ranging from seven days to 10 years.

More than 100 police officers were injured during the Jan. 6 riot.