Schumer attacked funding for ICE and Border Patrol, and Mullin answered with a sharp Fox News rebuke that pushed the Senate feud into full public view.
Todd Lyons will leave his role as acting ICE director on May 31, after nearly 20 years with the agency. DHS says he is headed to the private sector while the search for a replacement remains open.
President Trump removed DHS Secretary Kristi Noem and named Senator Markwayne Mullin to take over at the end of March. Senior adviser Corey Lewandowski is also leaving amid questions about a $200 million ad contract and who approved it. The move follows tense congressional testimony and media reports suggesting the contract process was limited to a few firms.