Acting Homeland Security Secretary Kevin McAleenan on Monday designated Customs and Border Protection Chief Operating Officer John Sanders as acting CBP commissioner, filling McAleenan's former post in the latest staffing shake-up at the Department of Homeland Security.

McAleenan, who was appointed acting DHS secretary following the resignation of Kirstjen Nielsen April 7, designated Sanders to take over “as the senior official performing the functions and duties of the commissioner” of CBP.

ACTING DHS SECRETARY MCALEENAN DESIGNATES TSA ADMINISTRATOR AS DHS DEPUTY

“John Sanders has proven instrumental to advancing CBP’s mission and organizational priorities across the agency,” McAleenan said in a statement. “In addition to bringing greater focus on the agency’s operational requirements, he has provided strategic direction and oversight to critical enterprise services and operations support functions across the agency.”

He added: “With John Sanders’ leadership, CBP will continue to excel, remain ever vigilant, and accomplish the mission with steadfast resolve.”

Monday's announcement caps a turbulent week for DHS. Last Sunday, President Trump announced Nielsen would resign from her post and be replaced with McAleenan.

But Nielsen’s resignation was only the beginning.

By last Monday, U.S. Secret Service Director Randolph ‘Tex’ Alles stepped down from his post after he was told to “prepare an exit plan,” in a signal, almost two weeks ago, that a transition in leadership at DHS was imminent.

CLICK HERE TO GET THE FOX NEWS APP

White House Press Secretary Sarah Sanders said Monday that the president had picked career Secret Service member James M. Murray to take over the agency in May. Alles will remain in his role until then.

Last Tuesday, DHS acting deputy secretary Claire Grady, who was technically next in line to replace Nielsen, resigned.

By last Wednesday, Nielsen announced that Immigrations and Customs Enforcement (ICE) Acting Director Ron Vitiello would be stepping down by the end of this week.

Last Thursday, McAleenan also designated the current head of the Transportation Security Administration, David Pekoske to be his acting deputy secretary at DHS. McAleenan also announced he would replace Pekoske at TSA with Patricia Cogswell, who currently serves as TSA’s acting deputy administrator.

SECRET SERVICE DIRECTOR TO STEP DOWN, ON HEELS OF NIELSEN RESIGNATION

Nielsen’s resignation came amid an influx of migrants at the U.S.-Mexico border. Nielsen was reportedly frustrated with the difficulty of getting other departments to help deal with the growing number of families crossing the border.

Administration officials, though, told Fox News last week that McAleenan best fits Trump’s requirement of being the “toughest cop” on the frontier, and that Nielsen had been viewed as resistant to some of the immigration measures pushed by the president and his aides.