A California man pleaded guilty on Tuesday to using a stun gun to attack Michael Fanone, the Washington DC police officer who was seriously injured while trying to defend the US Capitol from Donald Trump’s supporters on 6 January 2021.

Daniel Rodriguez, 40, of Fontana, admitted to taking part in the violent assault on Fanone, now a former Metropolitan police officer, after another rioter dragged Fanone into a crowd outside a tunnel where police were trying to beat back the mob.

Fanone, who lost consciousness and suffered a heart attack, was heard on camera screaming he had kids, in a desperate appeal for his life, as rioters beat him.

Rodriguez’s guilty plea came about two weeks before jury selection in his trial in federal court in Washington. He pleaded guilty to four felony charges including conspiracy and assaulting a law enforcement officer with a deadly or dangerous weapon.

An email seeking comment was sent to his lawyers. He was scheduled to be sentenced in May. Federal sentencing guidelines call for about seven to 10 years in prison.

Rodriguez admitted in an FBI interview in March 2021 that he drove a stun gun into Fanone’s neck. Rodriguez told agents he believed that he was doing the “right thing” and had been prepared to die to “save the country”. He cried as he spoke, saying he was “stupid” and ashamed of his actions.

Rodriguez’s attorneys tried to stop prosecutors using his FBI interview at trial, arguing that the agents used “psychologically coercive tactics”.

Authorities say Rodriguez and others were part of a Telegram group chat called “PATRIOTS 45 MAGA Gang” in the run-up to January 6, in which they advocated violence and discussed Trump’s claim of a stolen election.

In a post on 29 December 2020, Rodriguez wrote: “Congress can hang. I’ll do it. Please let us get these people dear God.”

At the Capitol, Rodriguez was part of the mob that pushed into the tunnel, prosecutors said. Inside, another rioter handed him the stun gun he would apply to Fanone’s neck. After assaulting Fanone, Rodriguez entered the Capitol through a broken window. Later, he texted his friends: “Tased the fuck out of the blue.”

Others charged with assaulting Fanone include Albuquerque Cosper Head, who wrapped his arms round Fanone’s neck and dragged him into the crowd. Head restrained Fanone while others attacked him. Head was sentenced in October to more than seven years in prison after pleading guilty to assault.

Fanone said at Head’s sentencing he suffered a heart attack and a traumatic brain injury, injuries that cost him his police career. He has written a book about his experience and testified before the House January 6 committee.

Another man, Kyle Young, who helped in the assault, was sentenced in September to seven years and two months in prison. Young grabbed Fanone by the wrist while others yelled “Kill him!” and “Get his gun!”

The sentences handed to Fanone’s attackers are among the longest handed down in relation to January 6.

Nearly 1,000 people have been charged with federal crimes. More than 500 have pleaded guilty, mostly to misdemeanors. Approximately 400 have been sentenced, with more than half given prison sentences ranging from seven days to 10 years.

The House January 6 committee made four criminal referrals to the Department of Justice regarding Trump’s incitement of the attack. Federal investigations continue.