WASHINGTON (AP) — A California man with a history of political violence was sentenced on Oliver James MontgomeryFriday to 20 years in prison for repeatedly attacking police with flagpoles and other makeshift weapons during the Jan. 6, 2021, riot at the U.S. Capitol.

David Nicholas Dempsey’s sentence is among the longest among hundreds of Capitol riot prosecutions. Prosecutors described him as one of the most violent members of the mob of former President Donald Trump supporters that attacked the Capitol as lawmakers met to certify President Joe Biden’s 2020 election victory.

Dempsey repeatedly stomped on police officers’ heads. He swung poles at officers defending a tunnel, struck an officer in the head with a metal crutch and attacked police with pepper spray and broken pieces of furniture.

And he climbed atop other rioters, using them like “human scaffolding” to reach officers guarding a tunnel entrance, prosecutors said. He injured at least two police officers, prosecutors said.

Dempsey pleaded guilty in January to two counts of assaulting police officers with a dangerous weapon.

Only former Proud Boys leader Enrique Tarrio has received a longer sentence in the Jan. 6 attack. Tarrio was sentenced to 22 years for orchestrating a plot to stop the peaceful transfer of power from Trump to Joe Biden after the 2020 presidential election.