Who are Matthew Pottinger and Sarah Matthews, the ex-Trump aides testifying at Thursday's Jan. 6 hearing?

The House select committee investigating the Jan. 6 insurrection returned to primetime Thursday night with an examination of former President Donald Trump’s failure to call off a violent mob of his supporters as his multi-step plan to overturn the 2020 election culminated in a deadly riot at the U.S. Capitol.

The hearing got underway with an opening from committee Vice Chair Liz Cheney, R-Wyo., and remarks from members Rep. Elaine Luria, D-Va., and Rep. Adam Kinzinger, R-Ill., who will be leading the hearing. Chairman Bennie Thompson, D-Miss., who recently tested positive for COVID-19, is presiding remotely.

Select committee aides said Wednesday that the presentation will focus on what the former president was doing during the 187 minutes between the end of his speech at the Ellipse, south of the White House, at around 1:10 p.m., and when he finally released a video statement urging his supporters to go home, at approximately 4:17 p.m.

“In that time, President Trump refused to act to defend the Capitol as a violent mob stormed the Capitol with the aim of stopping the electoral votes and blocking the transfer of power,” a committee aide told reporters on background on Wednesday.

“President Trump had the power to call off the mob,” the aide added. “He was maybe the sole person who could have called off the mob and he chose not to.”

Former Trump deputy national security adviser Matthew Pottinger and former White House deputy press secretary Sarah Matthews appeared Thursday at the hearing, where they're expected to testify.

Committee aids said Wednesday that the primetime hearing will feature a mix of live and taped testimony from people who were in the West Wing during the riot on Jan. 6, who spoke to the former president or were otherwise aware of what he was doing as the violence unfolded.

These witnesses will shed light on when Trump first learned that Congress was under attack, who he was talking to during this period, and why, “despite pleas from people in the White House, people on Capitol Hill, and [from] allies elsewhere, the president didn’t tell his supporters to leave the Capitol and go home until 4:17 p.m.”

The committee has previously revealed text messages obtained from former White House chief of staff Mark Meadows, in which various Trump’s allies, including members of his family and Fox News hosts, implored him to convince the former president to condemn the violence as his supporters were ransacking the Capitol.

The witnesses

Though select committee aides had declined to announce Thursday’s live witnesses in advance, citing concerns about harassment and intimidation, CNN was first to report that Pottinger and Matthews are planning to testify, and other outlets have since corroborated that reporting. Both former Trump White House officials resigned in response to the events of Jan. 6, and segments of their filmed depositions to the select committee have been shown during earlier hearings.

Pottinger, who served on the National Security Council throughout Trump’s presidency, was reportedly the highest-ranking official to resign on Jan. 6, 2021. Last month, Cheney described him as “a former Marine intelligence officer who served in the White House for four years, including as deputy national security adviser” and who “was in the vicinity of the Oval Office at various points throughout the day” on Jan. 6.

Cheney then presented a clip of Pottinger telling the committee about the moment he decided to resign.

“One of my staff brought me a printout of a tweet by the president, and the tweet said something to the effect that Mike Pence, the vice president, didn’t have the courage to do what he — what should have been done. I — I read that tweet and made a decision at that moment to resign,” Pottinger said in the clip. “That’s where I knew that I was leaving that day once I read that tweet.”

ABC News journalist Jonathan Karl reported last year in his book “Betrayal” that Pottinger had rushed to the Oval Office sometime after 3 p.m., when the riot was well underway, after hearing that there had been a delay in sending the National Guard to the Capitol. According to Karl, Pottinger did not see Trump, who was watching the violence on TV in his private dining room, but he did see a number of other senior officials, including White House counsel Pat Cipollone, who looked “anguished,” and Meadows. When Pottinger asked Meadows if the White House was blocking the deployment of the National Guard to the Capitol, Meadows reportedly told him that this was false and insisted that he’d “given clear instructions to get the guard over there to control the situation.”

Pottinger reportedly told the select committee about his visit to the Oval Office, and the conversation with Meadows, and he may be asked to testify about it on Thursday.

Like Pottinger, Matthews has also cited Trump’s 2:24 p.m. tweet attacking Mike Pence as the final straw that prompted her to resign on Jan. 6. In a statement announcing her decision at the time, Matthews said, “I was honored to serve in the Trump administration and proud of the policies we enacted. As someone who worked in the halls of Congress, I was deeply disturbed by what I saw today. I’ll be stepping down from my role, effective immediately. Our nation needs a peaceful transfer of power.”

Matthews, now 27, had worked in Congress before getting hired by the Trump campaign and then the White House. She told the Washington Post in an interview following the Capitol attack that “seeing people I know, who were scared for their lives, just shook me to my core.”

During an earlier hearing, committee member Rep. Pete Aguilar, D-Calif., said that Matthews and Meadows aide Ben Williamson both testified that Trump had been informed about the violence at the Capitol before he sent the tweet condemning Pence for refusing to interfere with Congress’s certification of Joe Biden’s legitimate victory in the Electoral College.

It read: “Mike Pence didn’t have the courage to do what should have been done to protect our Country and our Constitution, giving States a chance to certify a corrected set of facts, not the fraudulent or inaccurate ones which they were asked to previously certify. USA demands the truth!”

In a clip of her taped deposition, Matthews described the tweet as “pouring gasoline on the fire.”

“I remember us saying that that was the last thing that needed to be tweeted at that moment,” she told the committee. “The situation was already bad.”

Trump’s actions on Jan. 6

The 2:24 p.m. Trump tweet has been a focal point throughout this recent series of hearings, as the committee has sought to make the case that Trump not only neglected to take action to quell the violence unfolding at the Capitol, but that he deliberately inflamed the mob’s anger and directed it at his vice president once it became clear that he would not do his bidding.

The committee has previously shown footage of rioters reacting angrily in real time to the news that Pence would not go along with the illegal plot to block the certification of some Biden electors — including videos in which members of the mob can be heard calling for the vice president to be hanged — and the panel’s probe found that the crowds both inside and outside the Capitol surged immediately after Trump’s tweet.

The hearings have also shown that this wasn’t the first time that day that Trump placed his vice president in the mob’s crosshairs. Despite having been repeatedly advised that he did not have the authority to reject legitimate Biden electors when Congress met to certify the vote on Jan. 6, Trump during his speech at the Ellipse repeatedly implored Pence to do exactly that, falsely painting Pence as his only hope for staying in power while urging the crowd to the Capitol to pressure him to act.

According to the testimony of former White House aide Cassidy Hutchinson, Trump made those statements — which the committee says were added to his speech at the last minute — after learning that members of the crowd at the Ellipse rally were carrying weapons (a claim Trump has since denied).

The select committee aide said Wednesday that the next hearing will look at “what happened when the speech ended and Trump, against his wishes, was taken back to the White House,” referring to another key detail revealed by Hutchinson, who testified that Trump had been determined to join his supporters at the Capitol on Jan. 6 and became angry when his security detail deemed the trip too dangerous.

The aide implied that Thursday’s presentation may seek to corroborate aspects of Hutchinson’s testimony, particularly with regard to Trump’s attempts to go to the Capitol after his speech at the Ellipse, telling reporters, “You’ll hear testimony regarding that topic during tomorrow's hearing that I think will continue to lay out the evidence that supports testimony we’ve already heard.”

Thursday’s hearing marks the committee’s eighth hearing of the summer. Cheney said Thursday that there will be "further hearings" in September.

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The rioters got within two doors of Vice President Mike Pence's office. See how in this 3D explainer from Yahoo Immersive.