Washington DC - A man described by prosecutors as one of the "most violent" members of a pro-Donald Trump mob that stormed the US Capitol on January 6, 2021 was sentenced to 20 years in prison on Friday.

The sentence handed down to David Dempsey (37) of Santa Ana, California is the second longest for any of the nearly 1,500 people charged for their roles in the attack on Congress.

Enrique Tarrio, the former leader of the far-right Proud Boys group, was convicted of seditious conspiracy and sentenced to 22 years in prison.

The assault on the Capitol left at least five people dead and 140 police officers injured.

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It followed a fiery speech by then-president Trump to tens of thousands of his supporters near the White House in which he repeated his false claims that he won the 2020 election.

Prosecutors sought a term of nearly 22 years for Dempsey, noting in their sentencing memorandum that the former construction worker and fast-food restaurant employee had an extensive criminal record.

Dempsey pleaded guilty to two counts of assaulting police officers and was sentenced by Senior District Judge Royce Lamberth, an appointee of Republican president Ronald Reagan, to 20 years in prison and three years of supervised release.

Prosecutors, in their memo, called Dempsey "one of the most violent rioters, during one of the most violent stretches of time, at the scene of the most violent confrontations at the Capitol."

"Unlike other rioters who slowly pushed their way through the crowd towards the Capitol, Dempsey climbed atop his fellow rioters, using them like human scaffolding, thrusting himself to the front," they said.

Dempsey used his "hands, feet, flag poles, crutches, pepper spray, broken pieces of furniture, and anything else he could get his hands on, as weapons against the police," they said.

Trump faces four federal felony charges in Washington related to efforts to overturn the results of the 2020 election, but the case is unlikely to reach trial before the November presidential vote, in which he is once again the Republican candidate.