As a mob of his supporters assaulted the Capitol on Jan. 6, 2021, and a parade of officials — from the most senior to junior aides — scrambled to respond to an attack on the American government, former President Donald J. Trump sat in his dining room off the Oval Office, many of those officials have told congressional investigators, watching the violence on television and refusing to do anything to stop it.
The stunning accounts of the commander in chief choosing to take no action for more than three hours to protect the legislative branch were set to take center stage on Thursday at a marquee prime-time hearing of the House committee investigating the riot, the capstone on a series of public sessions to lay out its findings.
They were set to provide an up-close, panoramic view of what the former president was doing during the deadliest attack on the Capitol in two centuries — straight from the mouths of Mr. Trump’s top White House lawyer, a top national security adviser, his spokeswoman and his executive assistant.
The hearing was a closing argument of sorts in the case the panel has built against Mr. Trump, one whose central assertion is that the former president was derelict in his duty for failing to do all that he could — or anything at all, for 187 minutes — to call off the assault carried out in his name.
As evidence, the panel readied outtakes from Mr. Trump’s videotaped remarks of Jan. 7 that showed that, even after the mob violence, he struggled to condemn the assault or promise a peaceful transfer of power, according to a person familiar with the committee’s plans.
The hearing hardly marks the end of the committee’s work. The panel now plans to enter a second investigative stage, prepare a preliminary report and potentially hold additional hearings in the weeks to come.
“The investigation is still ongoing, if not maybe accelerating,” said Representative Elaine Luria, Democrat of Virginia and a member of the committee. “We’re gaining so much new information.”
Lawmakers were discussing using August, when Congress takes a lengthy recess, to prepare a preliminary report of their findings, tentatively scheduled to be released in September. But a final report — complete with exhibits and transcripts — could wait until December, just before the committee is set to dissolve at the start of a new Congress on Jan. 3, 2023.
For Thursday’s session, the panel turned to two military veterans — Ms. Luria, a Navy veteran, and Representative Adam Kinzinger, Republican of Illinois and a lieutenant colonel in the Air National Guard — to lead the questioning.
Representative Bennie Thompson, Democrat of Mississippi and the chairman of the committee, was presiding over the hearing remotely, after having tested positive for Covid-19 this week.
Key Revelations From the Jan. 6 Hearings
They were taking in-person testimony from two witnesses who resigned in disgust after observing Mr. Trump’s actions on Jan. 6: Matthew Pottinger, a Marine Corps veteran who was the deputy national security adviser and the highest-ranking White House official to resign on Jan. 6, and Sarah Matthews, a former White House press aide. Both abruptly left their jobs after the riot.
In a preview clip of the hearing that Mr. Kinzinger posted on Twitter on Thursday, a series of former Trump White House officials described how he sat in a dining room in the West Wing of the White House, watching television during the riot.
“He was always in the dining room,” Kayleigh McEnany, the former White House press secretary, told the panel.
Keith Kellogg, a retired lieutenant general who was Vice President Mike Pence’s national security adviser, told investigators that Mr. Trump, his chief of staff, Mark Meadows, and others were transfixed by the images on the screen, but that Mr. Trump was not taking any action to intervene.
“Everyone was watching the TV,” Mr. Kellogg testified.
When the panel’s investigators asked Pat A. Cipollone, the former White House counsel, whether the violence at the Capitol was visible on the screen as he talked to Mr. Trump, he replied simply, “Yes.”
Mr. Cipollone, who was in and out of the Oval Office that day, is expected to factor into the hearing several times, through clips of a videotaped interview that he gave under subpoena. Among the testimony he provided was an account of how paralyzed Mr. Meadows seemed at times.
At one point, Mr. Cipollone told the committee, he urged Mr. Meadows either to push Mr. Trump to make a public statement or do so himself, according to a person familiar with his testimony.
Mr. Cipollone also told the panel about receiving calls from members of the administration who wanted to quit that day. He was asked about Mr. Trump’s tweet condemning Mr. Pence while the rioters were rampaging through the Capitol, and about Mr. Trump’s eventual public statement shortly after 4 p.m., the person familiar with his testimony said.
At each of its hearings throughout June and July, the panel has presented evidence that lawmakers believe could be used to bolster a criminal case against Mr. Trump. The committee laid out evidence of a conspiracy to defraud the American people and Mr. Trump’s own donors; plans to submit false slates of electors that could lead to charges of filing false documents to the government; and evidence of a plot to disrupt the electoral count on Capitol Hill that suggest he could be prosecuted for obstructing an official proceeding of Congress.
The assertion that Mr. Trump was derelict in duty might not be the basis for a criminal charge, Ms. Luria said, but it raised ethical, moral and legal questions.
The committee has spent almost two months laying out its narrative of a president who, having failed in a series of efforts to overturn his defeat, directed a mob of his supporters to march to the Capitol after delivering a speech excoriating Mr. Pence for not interfering in Congress’s official count of electoral ballots to confirm Joseph R. Biden Jr.’s election as president.
His supporters have clung to the words he used in those remarks, when he told the crowd to go “peacefully and patriotically” to the Capitol. But the panel has revealed that Mr. Trump knew that his supporters were armed and threatening violence.
On Thursday, the committee was set to lay out its conclusion that Mr. Trump acted to intervene only after it became clear that the efforts of the mob to disrupt the electoral count were clearly failing.
He refused to do so until after 4 p.m. that day — and then only after hundreds of officers had responded to the Capitol to support the overrun Capitol Police force, and the tide had begun to against the mob, making it clear that the siege would fail.
Such evidence could add to a case the committee has been building that Mr. Trump was in favor of the mob’s actions that day, and only spoke out against the violence under pressure from his advisers.