Rep. Ken Buck (R-Colo.) took the stand Thursday in a case attempting to disqualify former President Trump from appearing on the 2024 ballot in Colorado, with the GOP congressman appearing as a witness on behalf of Trump campaign attorneys attempting to discredit the House Select Committee that investigated the Jan. 6, 2021, attack.

The case centers on whether Trump’s actions and speeches during and before the Jan. 6 riots could fall under a clause of the 14th Amendment that bans those who participate or assist in insurrection from federal office.

The plaintiffs have argued that Trump’s actions supported the rioters who eventually stormed the Capitol amid Congress’s official Electoral College count of the 2020 election, which Trump lost.

Buck described a chaotic scene on Jan. 6, as Capitol Police attempted to barricade the House chamber from approaching rioters.

“A police officer came to the microphone and said that tear gas had been dispersed. And we were advised that there were gas masks under our seats, and we should deploy those gas masks,” Buck said. “There was clear indication that there was a danger at that point.”

He said that he didn’t have phone reception and wasn’t aware of the riots, so he readied himself to assist police in fending off what he believed would be a small number of protesters.

“I came back to my office rather than the secure committee room, and I saw on TV what was going on and I thought, ‘Oh my goodness, there are a lot of people out there,’” he said.

Buck was the second lawmaker to take the stand in the case. Rep. Eric Swalwell (D-Calif.) testified Monday to recount his own experience that day.

Attorneys for Trump’s campaign also used Buck’s testimony in an attempt to criticize the House Select Committee on Jan. 6, whose report is a key piece of evidence used by plaintiffs in the Colorado case.

Only two Republicans — then-Reps. Liz Cheney (Wyo.) and Adam Kinzinger (Ill.) — were seated on the committee after then-Minority Leader Kevin McCarthy (R-Calif.) disallowed GOP members amid feuds with Democrats over the committee’s membership.

Buck revealed that he wanted to be on the committee and asked McCarthy, but he declined the offer.

“I asked Kevin if I could get his permission to seek to serve on that committee, because I thought it was important that witnesses were cross-examined and documents were challenged,” Buck said. “And Kevin told me that he did not want me serving on that committee, and he didn’t want any other Republicans serving on that committee.”

Trump attorney Scott Gessler described the final committee report as “incomplete” and with “one perspective,” claiming that it didn’t include Republicans’ perspective, at least not ones loyal to Trump, on the Capitol riots and implying that it should not be relied on as evidence.

Buck agreed with Gessler’s general sentiments, saying the report was just an exercise to support Democratic efforts to impeach Trump at the time.

“There was a political purpose to that report, as there is with almost everything in Congress, and the political purpose was ultimately to win elections and to paint the one side in as bad a light as possible,” Buck said. “And that’s why typically there is a minority report in an investigation like this.”

McCarthy pledged to investigate the committee’s findings, but that investigation did not hold the same subpoena powers as the committee itself.

“It’s my view that the people that would have been most challenging to the evidence and testimony were not seated, either by [former] Speaker [Nancy] Pelosi or Leader McCarthy, ultimately on the committee,” Buck continued. “I think in order to be able to judge someone’s culpability you’ve got to be able to hear both sides of the story. And in this case, there was not another side.”

Attorney Sean Grimsley argued for the plaintiffs that Buck’s testimony served little purpose.

“I think that President Trump’s lawyers brought you in here to impugn the integrity and the reliability of this report,” Grimsley told the congressman.

Buck announced Wednesday that he will not run for reelection.

The Hill’s Lauren Irwin contributed to this report.

Updated 5:04 p.m.