The Homeland Security Department announced Friday evening who will be acting secretary when John Kelly starts his new job as White House chief of staff on Monday.

In a brief statement, the department said that Elaine Duke, the deputy DHS secretary, will take his place until President Trump nominates a replacement, who will then need to be confirmed by the Senate.

Trump revealed Friday afternoon, in a string of tweets, that Kelly would be moving to the White House. He did not designate anyone else to serve as acting secretary in Kelly's stead.

Duke was sworn in as deputy secretary on April 10, and according to her DHS bio page had been serving as the department's chief operating officer and led "all efforts related to the strategic execution of DHS's vital missions."

Before that, Duke worked as the principal of Elaine Duke & Associates, LLC.

Kelly, a former Marine general, said in a statement of his own that he is "honored" to serve Trump as his new chief of staff, replacing Reince Priebus.