Cassidy Hutchinson, former Mark Meadows aide, speaks at surprise Jan. 6 hearing: Who is she?

The House committee investigating the Jan. 6 insurrection on Tuesday called a surprise public hearing featuring Cassidy Hutchinson, formerly a top aide to Donald Trump's last chief of staff, Mark Meadows.

Hutchinson was deposed multiple times by the committee during its year-long inquiry but on Tuesday she spoke publicly for the first time about what she had witnessed regarding the events before, during and after Jan. 6, 2021.

Sources told ABC News ahead of her testimony that Hutchinson, who is 26, was expected to put a voice to many of the internal White House interactions involving the events of Jan. 6 and offer significant insight into Meadows' actions and interactions with Trump.

Chair Bennie Thompson, D-Miss., convened the hearing shortly after 1 p.m. ET on Tuesday, with Hutchinson taking her seat as members took the dais. In brief opening remarks, Thompson explained information that she had needed to be shared with the American people "immediately" and hailed her courage.

"In recent days, the select committee has obtained new information dealing with what was going on in the White House on Jan. 6 and in the days prior -- specific, detailed information about what the former president and his top aides were doing and saying in those critical hours; firsthand details of what transpired in the office of the White House chief of staff," Thompson said.

Thompson had Hutchinson explain the proximity of her office -- and Meadows' office -- to the Oval Office. "Mr. Meadows and I were in contact pretty much throughout every day, consistently," she said.

She went on in her testimony to describe, among other details, how she was told about former President Trump's desire to go to the Capitol on Jan. 6 after he spoke at a rally near the White House -- and how Trump became furious when he was told it wasn't safe or advisable for him to be there.

Later on Tuesday afternoon, Rep. Ruben Gallego, D-Ariz., applauded for Hutchinson from his seat in the audience as she walked out for a brief recess.

A 2019 political science graduate of Virginia's Christopher Newport University, Hutchinson was an intern to House GOP Whip Steve Scalise, R-La., and Sen. Ted Cruz, R-Texas, in college before serving as a White House intern in 2018.

After graduating, she joined the Trump White House's Office of Legislative Affairs before working for Meadows as an executive assistant and later as a special assistant to the president.

"I have set a personal goal to pursue a path of civic significance," she told her alma mater in a 2018 interview after her White House internship.

Having already sat four separate times for closed-door depositions with the committee, Hutchinson has been featured in clips publicly displayed by the committee at previous hearings, including some in which she discussed members of Congress asking the White House for pardons.

During her earlier depositions, Hutchinson confirmed to committee investigators accounts that Meadows had burned documents in his office, according to sources. Meadows, who is fighting efforts by the House committee to testify, has not commented on those allegations and it's not clear if that behavior would have violated any record-keeping regulations.

In an April court filing, the committee revealed that Hutchinson had also told investigators that Meadows was aware of security "concerns" that indicated possible violence on Jan. 6 ahead of the rally near the White House where Trump spoke.

"I know that there were concerns brought forward to Mr. Meadows. I don’t know -- I don’t want to speculate whether or not they perceived them as genuine concerns, but I know that people had brought information forward to him that had indicated that there could be violence on the 6th. But, again, I’m not sure if he -- what he did with that information internally," she has said.

"I just remember [Tony Ornato, a Secret Service official and Trump White House deputy chief of staff] coming in and saying that we had intel reports saying that there could potentially be violence on the 6th. And Mr. Meadows said, 'All right. Let’s talk about it,'" she recalled, according to the filing, which also showed that Hutchinson had overheard members of the White House Counsel's Office saying that the plan to have alternate Trump electors meet and cast votes for Trump was not "legally sound."

Hutchinson's agreement to testify publicly comes after months of negotiations between the committee and her counsel, sources told ABC News. Hutchinson hired a new attorney, Jody Hunt, earlier this month to represent her as the latest public Jan. 6 hearings began.

At the start of the Trump administration, Hunt served as chief of staff to then-Attorney General Jeff Sessions. He later became the head of the Department of Justice's Civil Division.

Former Trump White House deputy press secretary Sarah Matthews showed support for Hutchinson ahead of her testimony.

"Just want to say how much admiration I have for the tremendous bravery Cassidy Hutchinson is displaying," Matthews wrote on Twitter. "Even in the face of harassment and threats, she is choosing to put her country first and tell the truth."

"This is what real courage, integrity, and patriotism looks like," Matthews added.

Matthews resigned from her position in the Trump administration on Jan. 6, 2021, saying then that she was "deeply disturbed" by what took place that day.

Former President Trump on Tuesday dismissed Hutchinson's testimony in characteristic fashion, posting on social media that "I hardly know who this person ... is, other than I heard very negative things about her (a total phony and 'leaker')."

"She is bad news!" he added.