The acting head of US Homeland Security, Kevin McAleenan, has resigned after six months in the post.
In a tweet, President Donald Trump said Mr McAleenan wanted to spend more time with his family. He said his replacement would be named next week.
Mr McAleenan (48) is the fourth person to serve as the head of Homeland Security during Mr Trump's tenure.
He has overseen the president's tough policies aimed at curbing immigration across the Mexican border.
However, analysts have described a turbulent relationship between the two and Mr McAleenan has criticized the tone of the immigration debate.
Recently he was shouted off stage by student protesters at a university in Washington DC.