Kirstjen Nielsen, whose background in cybersecurity sparked praise when she was named Department of Homeland (DHS) Secretary, reassigned Sunday.

“This afternoon I submitted my resignation to @POTUS and thanked him for the opportunity to serve in his administration. It’s been an honor of a lifetime to serve with the brave men and women of @DHSgov,” Nielsen tweeted, noting their dedication to protecting the U,S. from threats.

Last fall, it was widely rumored that Trump would soon give Nielsen the boot.
Once the top aide to White House Chief of Staff John Kelly when he headed DHS, Nielsen followed him to the White House, becoming his principal deputy chief of staff and helping him tighten up the West Wing. Her expertise included homeland security policy and strategy as well as cybersecurity, critical infrastructure and emergency management.

Under Nielsen, the department put resources into election security to protect the 2018 midterms. And last May, it released its long-awaited cybersecurity strategy to positive reviews from cybersecurity pros. She faced grilling by members of Congress, some of whom have bluntly reminded her that as Secretary the buck stops with her, and has had to tiptoe through a number of political minefields surrounding immigration and Russian interference.

She clearly frustrated lawmakers when said she hadn’t seen the intelligence reports that concluded that Russia’s meddling in the U.S. presidential election helped Trump gain the White House, Sen. Mark Warner, D-Va., the ranking member of the Senate Intelligence Committee, to email members of the press two reports and a copy of an indictment by Special Counsel Robert Mueller.

Calling Nielsen’s run at DHS “a disaster from the beginning,” Rep. Bennie Thompson, D-Miss., said her resignation “could not come at a worse time for the day to day management of the Department of Homeland Security and the over 220,000 employees that need leadership in order to best help keep the country secure.”Her departure leaves a void at DHS where the permanent deputy secretary of DHS position also remains open, Thompson said, urging that the positions are filled quickly.

U.S. Customs and Border Protection Commissioner Kevin McAleenan will be or acting DHS secretary, Trump tweeted Sunday.