Law enforcement officers have described fearing for their lives during the January attack on the US Capitol and living with “constant trauma” during the first hearing of the House investigation into the deadly assault, with prominent Republicans boycotting proceedings in an attempt to undermine any findings. In harrowing testimony on Tuesday, the officers described being crushed by violent pro-Trump rioters, threatened with their own service weapons, and being target by racist abuse. The special committee established by the Democratic House speaker, Nancy Pelosi, convened to investigate the circumstances surrounding the 6 January insurrection in Washington DC, when hundreds of Donald Trump’s supporters stormed the Capitol in an attempt to interrupt the certification of Joe Biden as president. “We must know what happened here at the Capitol,” Congresswoman Liz Cheney, a Trump critic and one of just two Republicans on the select committee, said in opening remarks. “We must also know what happened every minute of that day in the White House – every phone call, every conversation, every meeting leading up to, during and after the attack. Honorable men and women have an obligation to step forward.” The panel opened its first hearing on Tuesday with a focus on law enforcement officers who were attacked as rioters broke into the Capitol building, putting a human face on the violence and discrediting claims by Republican lawmakers that have played down or outright denied the severity of the attack. Sgt Aquilino Gonell of the US Capitol police (USCP) described how he was “crushed” by pro-Trump insurrectionists as he and colleagues tried to stop them entering the building. “I could feel myself losing oxygen and recall thinking to myself, ‘This is how I’m going to die,’ defending this entrance,” he told the committee. “For most people, January 6 happened for a few hours,” Gonell said. “But for those of us who were in the thick of it, it has not ended. That day continues to be a constant trauma for us.” Cheney asked Gonell about Trump’s claims that the crowd was full of “loving” people. “I’m still recovering from those hugs and kisses,” Gonell replied. “All of them were telling us ‘Trump sent us’,” he added, dismissing Trump’s baseless claims that leftwing demonstrators or the FBI were behind the attack. Michael Fanone, a Metropolitan police department officer who suffered a heart attack and a brain injury after being beaten by Trump supporters on 6 January, recounted how insurrectionists had threatened to use his gun against him. “I was grabbed, beaten, Tased, all while being called a traitor to my country. I was at risk of being stripped of and killed with my own firearm, as I heard chants of ‘Kill him with his own gun,’” Fanone said. “I can still hear those words in my head today.” Rebuking Republican lawmakers who have boycotted the hearings, Fanone said: “I feel like I went to hell and back to protect them and the people in this room.” Pounding his fist on the table in front of him, he said: “Too many are now telling me that hell doesn’t exist or that hell actually wasn’t that bad. The indifference shown to my colleagues is disgraceful.” US Capitol police officer Harry Dunn, who is Black, said he was repeatedly called the N-word as he sought to protect the Capitol. “Nobody had ever, ever called me a [N-word] while wearing the uniform of a Capitol police officer,” Dunn said, saying the racial slur. Dunn closed his testimony by expressing pride in his fellow USCP officers and encouraging them to protect their mental health as they deal with the fallout of the insurrection. The panel’s chairman, the Democratic congressman Bennie Thompson of Mississippi, told the police officers: “History will remember your name,” and warned there was “no place for politics and partisanship in this investigation”. Thompson said Tuesday’s hearing would “set the tone” of the inquiry, which will examine Trump’s role in the insurrection and the rightwing groups involved in coordination before the attack, including the white supremacists among them. It will also look at the security failures that allowed hundreds of people to breach the Capitol and send lawmakers running for their lives. Some of those who broke in were calling for the deaths of Pelosi and then-Vice President Mike Pence, who was hiding just feet away from the mob. The investigation into the 6 January attack has become a fiercely partisan issue in Washington. The House voted in May for an independent investigation that would have been evenly split between Democrats and Republicans, but the Senate blocked the move. That left Pelosi to create a select committee to conduct the investigation. Kevin McCarthy, the Republican House minority leader, picked five Republicans to sit on the committee, but Pelosi rejected Jim Jordan and Jim Banks’ nominations, prompting McCarthy to withdraw all five nominees. Both Jordan and Banks are staunch Trump allies who deny his role in the attack and objected to the certification of Biden’s win. Cheney had already been named to the panel by Pelosi. The speaker went around McCarthy again to appoint Republican congressman Adam Kinzinger, who is also a Trump critic, to the committee. Pelosi said Kinzinger “and other Republicans have expressed an interest to serve on the select committee … The two that I would not appoint are people who would jeopardise the integrity of the investigation, and there’s no way I would tolerate their antics as we seek the truth.” Kinzinger and Cheney were among the 10 House Republicans who voted for Trump’s second impeachment, and the pair were the only Republicans who voted to form the special committee. Both have cited Trump’s false claims of election fraud as a factor in the insurrection. Before the hearing, McCarthy again called the process a “sham”. Kinzinger told reporters on Tuesday that “for too long, we’ve been pretending that January 6 didn’t happen.” He said he never expected to be in this position, “but when you have these conspiracies that continue to thrive, when you have lies and misinformation that continue to thrive, it’s essential for us as members of Congress to get to the answers.” Shortly after the insurrection, almost every Republican denounced the violent mob, and Trump himself, who had told his supporters to “fight like hell” to overturn his election defeat. But many have changed their tone in recent months. Some have gone further, with the Georgia congressman Andrew Clyde saying a video of the rioters looked like “a normal tourist visit”. Last week, a Florida man became the first person to be sentenced to prison for his role in the attack. More than 570 people have been charged with taking part in the riot, during and after which seven people died.