A trucker who assaulted a police officer with a flagpole at the Capitol on January 6, 2021 was sentenced Monday to 52 months in federal prison.

The attack on the driver, Peter Stager, produced one of the most disturbing images to emerge from the attack on the Capitol. Mr. Stager, 44, of Conway, Ark., was captured on video hitting the officer, Blake Miller, with the flagpole in a fit of rage as Officer Miller lay face down in a crowd of other rioters with “no means of defending himself,” prosecutors wrote in court documents.

Mr. Stager was one of nine men charged with assaulting Officer Miller and two of his colleagues, Officers Carter Moore and Andrew Wayte, in a 90-second spree of violence that unfolded on the steps outside a tunnel on the Capitol’s Lower West Terrace. Officers who fell victim to attacks in a tunnel on the terrace and on the steps have repeatedly compared the violence to the hand-to-hand combat of a medieval battle.

After assaulting Officer Miller, prosecutors say, Mr. Stager was caught on video pointing at the Capitol and declaring: “Everybody there is a disgrace. That whole building is full of treasonous traitors. Death is the only remedy for what’s in that building.”

He went on to say, “Every one of those Capitol law enforcement officers, death is the remedy. That is the only remedy they get.”

In court papers filed before sentencing in Federal District Court in Washington, Stager’s attorneys told Judge Rudolph Contreras that their client, like many of the Jan. 6 defendants, experienced a traumatic childhood. During his early years, the lawyers wrote, Stager was homeless, sleeping under benches in California and stealing food from stores and dumpsters.

After Mr. Stager’s mother abandoned him and his siblings when he was around 6 years old, he ended up in foster care, lawyers said.

The attorneys told Judge Contreras that Mr. Stager was in Washington on January 6 only because of a scheduling conflict with his trucking company’s dispatch service. After delivering a load of produce to a destination near Washington, the attorneys wrote, he decided not to drive back to Arkansas with an empty truck, realizing he would make no money and would have to pay for fuel.

Instead, the lawyers said, Stager “decided to make the most of the situation” and attend President Donald J. Trump’s rally at the Ellipse in Washington on the morning of January 6.

“This decision is one that Mr. Stager will regret for the rest of his life,” the lawyers wrote.

As the crowd moved from Trump’s speech near the White House to the Capitol and became increasingly violent, “Mr. Stager’s emotional state was in shambles,” his attorneys wrote. Finally, “seeing red,” they said, he grabbed a flagpole from the ground and went after Officer Miller.

Mr. Stager apologized to the officer in a letter sent with the introduction of his lawyer, saying he had “no hate towards law enforcement, let alone anyone.”

Three of Mr. Stager’s co-defendants, Justin Jersey, Logan Barnhart and Mason Courson, were also sentenced on assault charges. Each of them was sentenced to prison terms of between three and five years, a relatively modest sentence for attacks on police.

Other rioters sentenced for assaulting officers have received some of the harshest sentences of any of the more than 1,000 people charged in connection with the attack on the Capitol.

A Pennsylvania welder who attacked officers with a chair and then a chemical sprayer was sentenced in May to more than 14 years in prison. The following month, a California man received more than 12 years in prison for twice shoving a Taser into the neck of Officer Michael Fanone.