Impeachment article has 200 cosponsors: US rep.

White House Deputy National Security Adviser Matthew Pottinger resigned on Wednesday, according to a White House official and a person familiar with his resignation, joining a slate of White House staff to resign in the wake of Wednesday's rioting at the U.S. Capitol.

The White House’s National Security Council did not respond to questions about Pottinger, who was an assistant to the president.

-ABC News' Chief White House Correspondent Jonathan Karl and Ben Gittleson

Former Attorney General Bill Barr, once one of President Trump's most loyal allies, is speaking out against his former boss in light of Wednesday's storming of the U.S. Capitol, saying in a statement that his conduct "was a betrayal of his office and supporters." 

“Orchestrating a mob to pressure Congress is inexcusable. The President’s conduct yesterday was a betrayal of his office and supporters," he said in a statement to the Associated Press, which was obtained by ABC News.

Barr resigned last month with five weeks remaining in Trump's term after months of growing tensions with Trump that culminated in Barr's refusal to announce investigations into Trump's political opponents and his public rebuke of Trump's baseless claims of widespread voter fraud in the 2020 election.

-ABC News' Alexander Mallin

“The White House grieves the loss of life that occurred yesterday and extends sympathies to their families and loved ones. We also continue to pray for a speedy recovery for those who suffered injury," the statement read.

Four people present during Wednesday's riots and the pro-Trump mob storming the Capitol have died, according to Washington, D.C. Metropolitan Police Department Chief Robert Contee. One woman was shot and killed by a U.S. Capitol Police officer when Trump supporters breached the building, forcing a lockdown with members of Congress inside. Another woman and two men suffered “medical emergencies” and subsequently died.

Neither Trump nor anyone more senior than Deere at the White House has publicly commented on the deaths.

-ABC News' Ben Gittleson

Former White House chief of staff Mick Mulvaney has resigned from his position as U.S. special envoy to Northern Ireland, telling CNBC during an interview Thursday morning he called Secretary of State Mike Pompeo Wednesday night with the news.

“I can't do it. I can't stay,” Mulvaney said. “It's a nothing thing. It doesn't affect the outcome. It doesn't affect the transition. But it's what I've got, right, and it's a position I really enjoy doing. But you can't do it. And I wouldn't be surprised to see more of my friends resign over the course of the next 24 to 48 hours."

Asked if, in retrospect, he considered himself an enabler of Trump, he said “it’s a fair question.”

“The answer is I don't know what I feel yet, entirely. I can tell you this, there are, most of us, almost all of us, except I guess the people who are on the inner circle right now who didn't sign up for what you saw last night.”

He said all of Trump’s “successes” -- “all of that went away yesterday, and I think you’re right to ask the question as to how did it happen.”

Mulvaney went on to say the issue now is that Trump’s inner circle consists of people like trade adviser Peter Navarro and personal attorney Rudy Giuliani.

“Clearly he is not the same as he was eight months ago, and certainly the people advising him are not the same as they were eight months ago, and that leads to a dangerous sort of combination as you saw yesterday," he said. "I imagine a lot of folks in the building, a lot of folks who served him from the beginning who are no longer in the beginning, are asking the same things this morning."

-ABC News' Ben Gittleson