Tom Bossert has been pushed out as White House homeland security adviser, multiple sources told CNN on Tuesday.
White House press secretary Sarah Sanders confirmed his departure in a statement.
"The President is grateful for Tom's commitment to the safety and security of our great country. Tom led the White House's efforts to protect the homeland from terrorist threats, strengthen our cyber defenses, and respond to an unprecedented series of natural disasters," Sanders said.
"President Trump thanks him for his patriotic service and wishes him well," she added.
Bossert's departure came a day after White House national security adviser John Bolton's first official day on the job.
There was no indication that Bossert planned to resign in recent days. On Sunday, Bossert was one of the administration's prominent faces on news shows discussing the administration's possible response to the alleged Syrian chemical weapons attack.
Bossert's most prominent role at the White House came after a series of devastating hurricanes hit several US states and Puerto Rico last fall, when Bossert served as the White House's point person for the emergency response and rebuilding efforts.
He also headed the administration's cybersecurity efforts, including its response to Russian interference in the 2016 election.
Bossert insisted as recently as Sunday that the US has been holding Russia accountable in "known and unknown ways" for the interference, citing in part the recent sanctions imposed on a list of Russian oligarchs.
Bossert also claimed on Sunday that "no voter in this country was influenced by those ads," referring to the Russian social media campaign during the 2016 election -- breaking from the US intelligence community's assessment, which did not examine the effect of the Russian campaign on voters.