From CBS News:
UPDATED ON: APRIL 7, 2019 / 7:00 PM / CBS NEWS
Department of Homeland Security Secretary Kirstjen Nielsen is resigning, President Trump announced in a tweet Sunday, as the president continues to fume over continued illegal border crossings. CBS News first reported Nielsen’s impending departure, which Mr. Trump announced after a 5 p.m. meeting with Nielsen at the White House.
Customs and Border Protection Commissioner Kevin McAleenan will serve as acting DHS secretary, Mr. Trump announced. …
One U.S. official told CBS News is it unlikely McAleenan would be nominated as Nielsen’s permanent replacement.