The House committee investigating the Jan. 6 attack laid out evidence on Thursday of how, as a mob of his supporters assaulted the Capitol, former President Donald J. Trump sat in his dining room off the Oval Office, watching the violence on television and choosing to do nothing for hours to stop it even as the lives of law enforcement officers, members of Congress and his own vice president were under threat.
In a final public hearing of the summer and the one of the most dramatic of the inquiry, the panel provided a panoramic account, narrated by sworn testimony from former aides and advisers, about a president who could not be moved to act until after it was clear that the riot had failed to disrupt Congress’s session to confirm his election defeat.
They detailed how the entire apparatus of government — the top White House lawyer and other senior West Wing advisers, low-level aides, Pentagon officials and even his own daughter — mobilized to respond to the attack, but the commander in chief willfully declined to do so.
“You’re the commander in chief. You’ve got an assault going on on the Capitol of the United States of America, and there’s nothing?” Gen. Mark A. Milley, the chairman of the Joint Chiefs of Staff, the nation’s highest-ranking military officer, told the panel. “No call? Nothing? Zero?”
In perhaps one of the most jarring revelations, the committee presented evidence that a call from a Pentagon official hoping to coordinate a response to the assault on the Capitol as it unfolded initially went unanswered because, according to one of Mr. Trump’s lawyers, “the president didn’t want anything done.”
And the panel played Secret Service radio transmissions and testimony that showed in chilling detail how close Vice President Mike Pence came to danger during the riot, including an account of members of his Secret Service detail being so rattled by what was unfolding that they were contacting family members to say goodbye.
Both pieces of testimony were provided by a former White House official whom the committee did not identify by name — and whose voice was altered to protect his identity — who was described as having had “national security responsibilities.”
The witness described an exchange between Eric Herschmann, a lawyer working in the White House, and the White House counsel, Pat A. Cipollone, about the call from the Pentagon.
“Mr. Herschmann turned to Mr. Cipollone and said ‘the president didn’t want anything done,’” the witness testified. “Mr. Cipollone had to take the call himself.”
The committee also played dramatic radio recordings over the span of 10 minutes, from 2:14 p.m. to 2:24 p.m., from Secret Service transmissions as Mr. Pence was being held in his office near the Senate chamber as they sought a route to safety to evacuate the vice president.
Key Revelations From the Jan. 6 Hearings
“Harden the door up,” one agent said. “If we’re moving, we need to move now,” another said. And at another point: “If we lose any more time, we may lose the ability to leave.”
And in a frightening moment over the radio traffic was a warning: “There is smoke. Unknown what kind of smoke it is.”
It 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. Thursday’s session asserted that Mr. Trump’s inaction during the riot was the final, glaring violation of his oath of office, coming at the end of a multipronged and unsuccessful effort to overturn his 2020 election loss.
White House officials recounted how the president declined to take the few steps down the hallway to the White House briefing room to call off the violence, instead tweeting an attack on Mr. Pence as he was fleeing for his life.
“I think that in that moment, for him to tweet out the message about Mike Pence, it was him pouring gasoline on the fire and making it much worse,” Sarah Matthews, a former White House press aide who resigned on Jan. 6 and was one of two witnesses who testified in person on Thursday.
The other was 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.
“That was the moment that I decided that I was going to resign, that that would be my last day at the White House,” Mr. Pottinger said, referring to Mr. Trump’s Twitter condemnation of the vice president. “I simply didn’t want to be associated with the events that were unfolding on the Capitol.”
The hearing hardly marked the end of the committee’s work. The panel now plans to enter a second investigative stage, prepare a preliminary report and hold additional hearings in September.
“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 said they would use 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.
“President Trump did not fail to act during the 187 minutes between leaving the Ellipse and telling the mob to go home,” Mr. Kinzinger said. “He chose not to act.”
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.