JOHN ROBERTS LIVE: Nielsen has resigned, Kevin McMaleenen[SPELL?] to replace. Roberts is not sure why.
TRUMP TWEETS:
Secretary of Homeland Security Kirstjen Nielsen will be leaving her position, and I would like to thank her for her service....
...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!