WASHINGTON (AP) — President Donald Trump on Thursday fired his embattled Homeland Security Secretary Kristi Noem, after mounting criticism over her leadership of the department, including the handling of the administration’s immigration crackdown and disaster response.

Trump, who said he would nominate Oklahoma Republican Sen. Markwayne Mullin in her place, made the announcement on social media after Noem faced a two-day grilling on Capitol Hill this week from GOP members as well as Democrats.

Noem’s departure marks a stunning turnaround for a close ally to the president who was tasked with steering his centerpiece policy of mass deportations. But she appeared to increasingly become a liability for Trump, with questions arising over her spending at her department and over her conduct in the aftermath of the shooting deaths of two protesters in Minneapolis earlier this year.

Trump said he’ll make Noem a “Special Envoy for The Shield of the Americas,” a new security initiative that he said would focus on the Western Hemisphere.

Noem, who appeared at a law enforcement event in Nashville, Tennessee, moments after Trump’s announcement, did not address her ouster there. She read from prepared remarks and was not asked by attendees about the development.

Later, in a social media post, she thanked Trump for the new appointment and touted her accomplishments as secretary.

“We have made historic accomplishments at the Department of Homeland Security to make America safe again,” she wrote.

CT senators Murphy and Blumenthal respond

Connecticut’s Democratic senators agreed with Noem’s ouster, but they cautioned that the U.S. Department of Homeland Security would need to undertake a vastly different approach to how it operates.

U.S. Sen. Chris Murphy, D-Conn., said he doesn’t believe Noem’s departure will ultimately change how DHS operates, including its handling of Trump’s immigration crackdown. That’s because he sees White House deputy chief of staff Stephen Miller as running the show.

“I think it’s good that she’s gone. She was horrible, but she wasn’t in charge to begin with. So that’s Stephen Miller’s department and it’ll continue to be Stephen Miller’s department,” Murphy told reporters at the U.S. Capitol.

“Changing the nameplate on the door doesn’t change the fact that they are committed to using DHS to terrorize communities and migrants in this country,” he added.

U.S. Sen. Richard Blumenthal, D-Conn., said he hopes the next person who assumes the helm at Homeland Security can turn the page on an agency and secretary who had come under fire, most prominently over ICE’s surge of federal agents in Minneapolis.

“Kristi Noem has richly deserved her firing,” Blumenthal said while making his way to Senate votes. He described her as “condoning atrocities” and “peddling falsehoods,” adding, “The past illegalities, brutality and violence, plainly and blatantly breaking the law and the Constitution, all have to be completely put in the past.”

At the Senate Judiciary Committee earlier this week, Blumenthal pressed Noem over federal agents who have arrested, detained or injured U.S. citizens. During that hearing, she defended the practices of ICE and Border Patrol agents. Noem also didn’t know the specifics of some of the cases involving American citizens.

“Whoever follows Kristi Noem is going to have to be totally and radically different in their approach to running this agency, changing the person at the top is no substitute for changing the practices and power structure of a department that’s out of control,” Blumenthal said.

The administration’s immigration crackdown faced criticism, especially in Minnesota

Noem is the first Cabinet secretary to leave during Trump’s second term. Her tenure looked increasingly short-lived after hearings in Congress this week where she faced rare but blistering criticism from Republican lawmakers. One particular point of scrutiny was a $220 million ad campaign featuring Noem that encouraged people in the country illegally to leave voluntarily.

Noem told lawmakers that Trump was aware of the campaign in advance, but Trump disputed that in an interview Thursday with Reuters, saying he did not sign off on the ad campaign.

Noem has faced waves of criticism as she’s overseen Trump’s immigration crackdown, especially since the shooting deaths of the two protesters in Minneapolis at the hands of immigration enforcement officers. The former South Dakota governor was also criticized over the way her department has spent billions of dollars allocated to it by Congress.

Her department, DHS, has been at the center of a funding battle in Congress over immigration enforcement tactics and has been shut down for 20 days, although many of the employees are continuing to work, often without pay.

Even before Noem’s appearance before key congressional committees this week, Republican lawmakers had been anticipating the secretary’s eventual ouster, particularly after her handling of the immigration enforcement crackdown in Minneapolis.

As they tried to end the ongoing Homeland Security shutdown, Senate Republicans had noted privately to Democratic senators that Noem was likely on her way out and that that should prompt Democrats to move forward with agreeing to fund the department again, according to two people familiar with the discussions.

Democrats did not see that as an actual concession by Republicans, considering Noem was becoming a political liability for the GOP, said the people, who spoke on condition of anonymity to discuss private negotiations.

DHS leadership changes come at a pivotal time

Aside from immigration, Noem also faced criticism — including from Republicans — over the pace of emergency funding approved through the Federal Emergency Management Agency and for the Trump administration’s response to disasters.

Mullin would need to be confirmed by the Senate, but under a federal law governing executive branch vacancies, he would be allowed to serve as an acting Homeland Security secretary as long as his nomination is formally pending.

Voting in the Senate just after Trump’s announcement, Mullin said he has “no idea” how quickly his nomination will move.

“The president and I are good friends. So we look forward to working closer with the White House, and obviously I’m gonna be over there a lot more,” he said.

Mullin would need to be confirmed by the Senate, but under a federal law governing executive branch vacancies, he would be allowed to serve as an acting DHS secretary as long as his nomination is formally pending.

Mullin would take over the third-largest department in government that has responsibility for carrying out Trump’s hardline immigration agenda. And he would assume the role at a pivotal time for that agenda.

Immigration enforcement during the first year of Trump’s administration was largely defined by high-profile, made-for-social-media operations with flashy names, often led by Border Patrol commander Gregory Bovino, who reported directly to Noem. Noem herself often went out on those operations, riding along with officers when they went out to make arrests.

But those high-profile operations in places like Los Angeles, Chicago and Minneapolis often led to clashes with activists and protesters that were captured on video and drove opposition to the president’s immigration agenda.

That culminated with the shooting deaths in Minneapolis after which Trump shuffled leadership of the operation. The number of officers there was drawn down shortly after.