Donald Trump knew supporters had weapons when he urged them to storm the Capitol to overturn the 2020 election, a former White House aide has said.
Ex-aide Cassidy Hutchinson testified to the committee probing the 6 January 2021 riots that Mr Trump and his top staff knew the potential for violence.
But a planned rally went ahead, with Mr Trump saying the armed attendees were "not here to hurt me".
The president also demanded to join the march on the Capitol himself, she said.
Up until now, the congressional panel was missing testimony from inside the room - someone who could offer a first-hand account of the situation in the White House in the critical hours before and during the attack.
But at its sixth hearing on Tuesday - hastily announced with what the committee said was the revelation of new evidence - Ms Hutchinson, 25, filled in the blanks.
As principal advisor to Mr Trump's chief of staff Mark Meadows, she sat just feet from the Oval Office and spoke daily with Mr Meadows.
She recounted that several top officials warned repeatedly that Mr Trump's rally on 6 January could spiral out of control.
During her testimony, Ms Hutchinson said:
- Days before the attack Mr Meadows predicted that things "could get real, real bad" on 6 January
- When told on 6 January that Mr Trump's supporters had brought guns, knives and other weapons with them, Mr Meadows barely looked up from his phone and asked "anything else?"
- Mr Trump was angered when told that Secret Service agents were turning away his supporters because they were armed and setting off security devices
- "They're not here to hurt me" and "let them in", Mr Trump said
- Director of National Intelligence John Ratcliffe told the White House the event could be "dangerous for the president's legacy"
- White House counsel Pat Cipollone expressed concerns it would look like the White House was inciting a riot
As she was speaking, Mr Trump denied her account on his Truth Social online platform, saying: "I didn't want or request that we make room for people with guns to watch my speech. Who would ever want that?"
Other parts of Ms Hutchinson's testimony portrayed the former president as reacting angrily when he was upset by certain events.
When attorney general William Barr dismissed the president's election fraud claims in a December 2020 interview, Mr Trump smashed crockery in a rage - which Ms Hutchinson said he had done in the past - and sent ketchup splattering onto the walls of a White House dining room.
And after his supporters marched to the Capitol, Mr Trump insisted he wanted to join them, she said.
Mr Trump lunged for the steering wheel of his presidential limo after he was told he could not be taken to the Capitol, she said she was told by another aide. He was eventually returned to the White House.
Mr Trump denied the claim that he attempted to commandeer his limousine, writing online: "Wouldn't even have been possible to do such a ridiculous thing".
A source close to the Secret Service told CBS News that the driver and another officer are willing to testify that the former president did not try to grab the steering wheel.
Ms Hutchinson also said that her boss, Mr Meadows, had sought a pardon from the president after the riot.
During her testimony, she recalled seeing Mr Trump's tweet, condemning his vice-president, Mike Pence, for lacking the "courage" to overturn the election results.
Mr Pence rejected claims he had the power to halt the congressional certification of the election.
"As an American I was disgusted... It was unpatriotic, it was un-American, and you were watching the Capitol building get defaced over a lie," she said.
In a statement following her testimony, her lawyers said "her duty" compelled Ms Hutchinson to testify to the committee.
Ms Hutchinson is one in a series of Republicans and former White House staffers to co-operate with the congressional probe.
Vice chairwoman Liz Cheney, one of only two Republicans on the committee, praised her co-operation with the inquiry, saying that Trump allies have pressured fellow Republicans to "continue to be a team player".
The select committee has conducted a nearly year-long investigation into how Trump supporters invaded Congress to disrupt lawmakers as they certified Democrat Joe Biden's election victory.
It plans to continue its work with at least two more public hearings next month.