Who is Markwayne Mullin, Trump's new pick for Homeland Security secretary?

US President Donald Trump has announced Oklahoma Senator Markwayne Mullin will be the new Homeland Security secretary, replacing the agency's embattled head Kristi Noem.

The first-term senator, a former mixed martial arts fighter, has been a supporter of Trump and his policies since coming to Washington.

Mullin, known for his fiery personality, will be the second Homeland Security chief in Trump's second administration. The Senate would need to confirm Mullin to the post.

The senator has been complimentary of the Department of Homeland Security's (DHS) efforts to detain undocumented immigrants - a fixture of the Trump administration's policy and a focus for Noem before she was ousted.

Mullin is among the Republicans who have been critical of the ongoing partial US government shutdown, which has allowed funding to lapse from the DHS.

"What is actually happening right now with the Democrat Party by this political theatre, by shutting down DHS for something that you even admitted yourself can't be done," Mullin told CNN last month. "They're not stopping [Immigration and Customs Enforcement (ICE)] from doing their job."

Should he be confirmed, Mullin will head an agency that has faced increased criticism in recent months, particularly in the wake of two US citizens being killed by federal immigration officials in Minnesota.

He has previously supported Homeland Security policy and the administration's immigration crackdown.

"Obstructing federal law enforcement is a felony. Most Americans follow ICE instructions without thinking twice," Mullin posted on social media following the death of Alex Pretti, who was shot dead by immigration agents in Minneapolis.

"These patriots are doing a difficult job under an 8,000% rise in death threats," he added.

Mullin was sworn in as a US senator in 2023.

Over the past two decades, Mullin, father to six children, worked alongside his wife to grow his family plumbing business, according to his website.