One of the Washington DC police officers who gave emotional testimony to Congress about the violence of the 6 January Capitol insurrection said on Wednesday he had received a vulgar voicemail threatening his life while he was on the stand, adding: “This is what happens when you tell the truth in Trump’s America.”

Michael Fanone, who suffered a heart attack after being beaten and Tasered by supporters of the former president while defending the Capitol, also criticized Republicans, including the House minority leader, Kevin McCarthy, who chose not to observe Tuesday’s opening day of the select committee’s investigation.

McCarthy, who has walked back his earlier assertion that Donald Trump “bears responsibility” for the insurrection and refused to let Republican members of Congress participate in the hearings, was among a number of senior party officials who claimed they were “too busy” to watch.

“I’ve heard reports that many reported that they were not watching my testimony, or that of my colleagues. I find that very telling,” Fanone said on CNN’s New Day on Wednesday morning.

“You have people like Kevin McCarthy, whose members have been downplaying or denying events of that day. It’s not politically advantageous for him to continue to have to answer questions about the 6 January insurrection, which was at least in part incited by the leader at the time of his political party.”

Fanone also revealed details of the voicemail that he received on Tuesday morning as he was giving evidence, a lengthy rant from a Trump supporter including racial slurs, death threats and accusations that he was “a traitor”. The message, he said, reflected the increasing anger, fomented largely by the previous president and his acolytes, towards those who chose to speak out.

“I thought about all the other public servants whose service to this country in the military have been disparaged or besmirched by Trump and his supporters simply because they told the truth,” Fanone said.

“I think about the doctors who fought to get accurate information out about a pandemic that we were experiencing, and how they were disparaged by the former president and his supporters, simply for trying to save American lives. I realized I’m in good company.”

Republican Congress members who skipped the hearing gave a variety of reasons for not attending or watching, inquiries by the Washington Post revealed.

McCarthy claimed he was “booked in all these different meetings”, while Elise Stefanik, who became Republican conference chair after members ousted the Wyoming congresswoman Liz Cheney for voting for Trump’s impeachment, would not say if she watched.

Cheney and the Illinois congressman Adam Kinzinger, both prominent Trump critics, are the only two Republicans who accepted House speaker Nancy Pelosi’s invitation to serve on the select committee.

Meanwhile, Jim Jordan, the Ohio congressman and outspoken Trump defender who was one of McCarthy’s original picks, but was rejected by Pelosi, told reporters he was also tied up with committee meetings.

The Montana congressman Matthew Rosendale told ABC News that he watched, but only to see Cheney’s opening statement, which referred to the “unbelievable violence and the inexcusable and intolerable cruelty” that the Capitol police officers faced on 6 January.

“I was quite disappointed,” Rosendale said.

During the hearing on Tuesday, Fanone, who has needed several months of physical and mental therapy to help him recover from the trauma he endured, was critical of Republicans who chose not to be present, or who had downplayed the insurrection.

“I feel like I went to hell and back to protect them, and too many in this room … are now telling me that hell doesn’t exist or hell actually wasn’t that bad,” he said.

“The indifference shown to my colleagues is disgraceful.”