WASHINGTON — Cassidy Hutchinson, a former aide to President Donald J. Trump’s final chief of staff, delivered explosive testimony on Tuesday to the House committee investigating the Jan. 6 attack on the Capitol, providing a vivid minute-by-minute account of heated confrontations she witnessed play out in the White House.

Ms. Hutchinson testified that Mr. Trump knew the crowd he had amassed in Washington on Jan. 6, 2021, was armed and could turn violent but encouraged them to march on the Capitol anyway, and said she had heard that he had lunged at one of his Secret Service agents when he was told he could not join his supporters on Capitol Hill.

And she detailed how her boss, Mark Meadows, was seemingly unmoved by reports of violence on Capitol Hill, even as other aides to Mr. Trump grew agitated.

Below is a timeline of the key moments from Jan. 6, as described in her testimony.

Around 10:00 a.m. or 10:15 a.m.

Mr. Meadows and Mr. Trump are told that attendees at the president’s rally are armed.

Ms. Hutchinson and Anthony M. Ornato, the deputy White House chief of staff, met with Mr. Meadows to tell him that law enforcement was reporting that multiple individuals were arriving at Mr. Trump’s rally on the Ellipse carrying weapons including knives, guns, bear spray, body armor, spears and flagpoles.

“Tony relayed to me something to the effect of, ‘These f-ing people are fastening spears to the end of flagpoles,’” Ms. Hutchinson testified.

Mr. Meadows appeared unmoved, asking only if Mr. Ornato had relayed the information to the president. Mr. Ornato replied that he had, Ms. Hutchinson said.

Early that afternoon, Ms. Hutchinson texted Mr. Ornato that Mr. Trump was “furious” that rallygoers were being forced to pass through magnetometers, according to messages she provided to the committee. Backstage at the rally on the Ellipse, she overheard Mr. Trump angrily tell aides to let his supporters into the event space, concerned that the area looked empty.

Mr. Trump, she testified, said “something to the effect of, ‘I don’t f-ing care that they have weapons. They’re not here to hurt me. Take the mags away. Let the people in, they can march to the Capitol from here.’”

Around 1 P.M.

White House aides learn that Capitol Police were at risk of becoming ‘overrun’ by rioters.

While Mr. Trump was addressing his supporters at the Ellipse, backstage, Ms. Hutchinson learned that Secret Service agents were reporting that Trump supporters mobbing the Capitol were getting close to the building, and that it was becoming clear that “security at the Capitol would not be sufficient” to hold them off, she testified.

When she got to Mr. Meadows to relay that Capitol Police were being “overrun” by rioters, he “almost had a lack of reaction,” Ms. Hutchinson testified.

“I remember him saying, ‘All right,’” she said. “Something to the effect of, ‘How much longer does the president have left in his speech?’”

Around 1:10 P.M.

Representative Kevin McCarthy of California, the House Republican leader, angrily calls Ms. Hutchinson and tells her not to let Mr. Trump come to the Capitol.

After Mr. Trump told rally attendees that he planned to march to Capitol Hill with them, Mr. McCarthy furiously called Ms. Hutchinson, she testified, demanding to know why he had been misled.

“You told me this whole week you aren’t coming up here. Why would you lie to me?” Mr. McCarthy said, according to Ms. Hutchison.

Ms. Hutchinson said she replied: “I wasn’t lying to you, sir. We’re not going to the Capitol.”

“He said, ‘Well, he just said it onstage, Cassidy. Figure it out. Don’t come up here,’” she testified.

After Ms. Hutchinson returned to the White House from the rally, she said, Mr. Ornato and the head of Mr. Trump’s security detail, Bobby Engel, described to her a shocking scene that had unfolded inside the president’s vehicle.

Told after his speech that he could not go to the Capitol because of security concerns, Mr. Trump became “irate” and said “something to the effect of, ‘I’m the f-ing president, take me up to the Capitol now,’” Ms. Hutchinson testified she had been told.

When Mr. Engel responded that they needed to go back the White House, Mr. Trump “reached up toward the front of the vehicle to grab at the steering wheel,” and lunged at him, Ms. Hutchinson said.

Around 2 p.m. to 2:05 p.m.

White House counsel warns Meadows: ‘Something needs to be done or people are going to die.’

Ms. Hutchinson testified that as she and other White House aides were glued to the television, watching the scene at the Capitol grow increasingly violent, Pat Cipollone, the White House counsel, stormed into Mr. Meadows’s office, and said something to the effect of, “The rioters have gotten to the Capitol, Mark. We need to go down and see the president now.”

Ms. Hutchinson testified that Mr. Meadows looked up at Mr. Cipollone and said: “He doesn’t want to do anything, Pat.”

Mr. Cipollone replied, according to Ms. Hutchinson: “Something needs to be done or people are going to die and the blood’s going to be on your f-ing hands. This is getting out of control. I’m going down there.”

After Mr. Meadows and Mr. Cipollone emerged from a meeting with Mr. Trump in the West Wing dining room, Mr. Cipollone was still frustrated, Ms. Hutchinson said, recounting a conversation between the two men that she overheard.

“I remember Pat saying something to the effect of, ‘Mark, we need to do something more. They’re literally calling for the vice president to be f-ing hung,’” she testified. “And Mark had responded something to the effect of, ‘You heard him, Pat. He thinks Mike deserves it. He doesn’t think they’re doing anything wrong.’”

2:24 P.M.

Mr. Trump tweets that Mr. Pence ‘didn’t have the courage’ to overturn the election.

Mere minutes after the mob breached the Capitol, Mr. Trump put out a broadside attacking Vice President Mike Pence for refusing to reject Joseph R. Biden Jr.’s electoral victory, posting on Twitter: “Mike Pence didn’t have the courage to do what should have been done to protect our Country and our Constitution.”

In some of the most emotional testimony of the day, Ms. Hutchinson recalled seeing the post and feeling “disgusted.”

“It was unpatriotic. It was un-American. We were watching the Capitol building get defaced over a lie,” she said.

Around 3 p.m.

White House aides draft a statement denouncing the rioters who breached the building, but it is never issued.

After Mr. Meadows and some of Mr. Trump’s attorneys huddle in a meeting, Mr. Meadows began dictating a statement to Ms. Hutchinson that they hoped the president would release, calling the actions of rioters who breached the Capitol “illegal.”

The statement was never released.