The Trump administration’s most controversial enforcer is out.

President Donald Trump abruptly fired Homeland Security Secretary Kristi Noem on Thursday, ending a turbulent tenure marked by deadly immigration operations, political infighting and mounting pressure from both parties in Congress.

Noem becomes the first Cabinet secretary to depart Trump’s second-term administration. But her exit is less a quiet resignation than a dramatic reshuffling of power inside an administration still defined by its hard-line immigration agenda.

Trump announced on Truth Social that Sen. Markwayne Mullin of Oklahoma would take over the Department of Homeland Security beginning March 31, pending Senate confirmation.

“I am pleased to announce that the Highly Respected United States Senator from the Great State of Oklahoma, Markwayne Mullin, will become the United States Secretary of Homeland Security,” Trump wrote.

At the same time, the president revealed that Noem would not be leaving the administration entirely. Instead, she will move into a newly created role titled “Envoy for The Shield of the Americas,” a position Trump described as leading a sweeping Western Hemisphere security initiative.

Still, the sudden shift caps what officials privately describe as a disastrous year for the South Dakota Republican.

An administration official told NBC News that the president’s decision came after “a culmination of her many unfortunate leadership failures,” including the fallout from immigration raids in Minneapolis, controversial advertising campaigns and ongoing tensions within the department.

Behind the scenes, critics inside the administration reportedly grew frustrated with what they viewed as constant drama surrounding Noem’s leadership.

Officials cited allegations of infighting with agency leaders, staff mismanagement and repeated clashes with top figures at Customs and Border Protection and Immigration and Customs Enforcement.

The final straw may have been a series of congressional hearings earlier this week.

During testimony before lawmakers, Noem defended a $200 million Department of Homeland Security advertising campaign urging migrants in the United States illegally to voluntarily deport themselves. The ads prominently featured Noem and were broadcast largely in English.

When senators questioned the program, Noem said the president had approved the campaign.

The White House quickly contradicted her.

“POTUS did not sign off on a $220 million ad campaign. Absolutely not,” a White House official told reporters.

The tension underscored a widening rift between Noem and the president’s inner circle.

Her leadership was already under intense scrutiny following two fatal shootings involving U.S. citizens during federal immigration operations in Minneapolis. Critics blasted the deployment of federal troops during those operations and questioned the tactics used by agents.

Noem further inflamed the situation when she referred to the two victims as “domestic terrorists,” refusing to retract the comment even as investigations into the killings continued.

The controversy sparked rare bipartisan criticism.

Republican Sens. Thom Tillis and Lisa Murkowski publicly called for her resignation earlier this year, with Tillis saying he could not “think of any point of pride” from her tenure.

While Noem was delivering a keynote speech to law enforcement officials in Nashville on Thursday, the political earthquake was unfolding in Washington.

She made no mention of her removal during the speech.

Instead, she thanked law enforcement leaders and spoke about cooperation between federal agencies.

Shortly after Trump’s announcement, Noem responded on social media, thanking the president and defending her time leading the department.

“In this new role, I will be able to build on the partnerships and national security expertise I forged over the last 13 months as Secretary of Homeland Security,” she wrote.

Her departure also appears to signal the end of another controversial presence inside DHS.

Corey Lewandowski, a longtime Trump adviser who had been working closely with Noem, is also expected to leave the department amid scrutiny from lawmakers over his role in approving federal contracts and grants.

Meanwhile, the man tapped to replace her, Markwayne Mullin, appeared genuinely surprised by the call.

During a Senate Republican lunch Thursday, Mullin reportedly received a phone call from the White House switchboard, abruptly left his meal behind and rushed out of the room.

“I’ve got to be honest with you,” Mullin later told reporters. “I wasn’t expecting the call today.”