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 Noem “has served us well, and has had numerous and spectacular results (especially on the Border!).” He said he was making her 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.

White House press secretary Karoline Leavitt said the administration will work with the GOP-led Senate to get Mullin, whom she called “extraordinarily qualified,” confirmed to lead DHS “as soon as possible.”