By Steve Neavling
Homeland Security Secretary Kirstjen Nielsen resigned Sunday to address the Trump administration’s concern over illegal immigration.
In a tweet Sunday, Trump thanked Nielsen for her service and announced that Kevin McAleenan, the U.S. Customs and Border Protection commissioner, would become the acting DHS secretary.
….I am pleased to announce that Kevin McAleenan, the current U.S. Customs and Border Protection Commissioner, will become Acting Secretary for @DHSgov . I have confidence that Kevin will do a great job!
— Donald J. Trump (@realDonaldTrump) April 7, 2019 
McAleenan is a longtime border official who has fostered a good relationship with Congress and the Trump administration.
Nielsen met with Trump at the White House on Sunday, unaware she was going to be forced to resign, two people familiar with the decision told the Associated Press. 
The sources said the move was part of a shakeup over the number of Central American families spilling across the southern border.
In her resignation letter,  Nielsen never mentioned a riff with the Trump administration and said she was proud of her service and the employees at DHS.
“It has been my great honor to lead the men and women of the Department as its sixth Secretary,” Nielsen wrote. “I could not be prouder of and more humbled by their service, dedication, and commitment to keep our country safe from all threats and hazards.”