Donald Trump fired Homeland Security Secretary Kristi Noem on March 5, sparking new controversy surrounding her tenure. Trump announced that Republican Senator Markwayne Mullin will succeed Noem at the Department of Homeland Security (DHS).

Trump announced on Truth Social that Mullin will take over as Secretary of Homeland Security on March 31.
He further said that Noem will serve in the newly created “Envoy to the Americas Shield” role related to the new regional security plan that his administration intends to present in Florida this weekend.
Possible reasons for Kristi Noem’s firing
Scandals have mounted during Noem’s tenure, eroding support inside and outside the government. The Department of Homeland Security has been under heavy criticism in the months since two U.S. citizens were shot to death by federal agents during an immigration enforcement operation in Minneapolis earlier this year. The incident sparked protests and calls for an investigation into the agency’s methods.
One of the immediate triggers for Noem’s firing was the controversy in Congress over funding for the department.

