(CNN) President Donald Trump's longtime personal aide John McEntee was fired because he is currently under investigation by the Department of Homeland Security for serious financial crimes, a source familiar with his firing told CNN.
The charges are not related to the President, the source said.
Minutes after news of his departure broke, the Trump campaign announced McEntee would be joining the reelection effort as a senior adviser for campaign operations.
McEntee was escorted from the White House on Monday, three sources with knowledge of the matter told CNN. Two sources initially said McEntee was pushed out because of issues with his security clearance, but another source familiar with the matter later said he had been granted a permanent security clearance before was abruptly fired.
McEntee declined a CNN request to comment.
"We don't comment on security clearances or personnel issues," White House press secretary Sarah Sanders told CNN in a statement.
White House aides were stunned when they learned of McEntee's sudden departure, two sources tell CNN. His abrupt firing came out of nowhere and there was no warning, they said.
McEntee was one of few aides who did not have their access to the President limited when John Kelly became the chief of staff last fall. He was a near-constant presence in the West Wing, and was one of a select group of staffers who were often summoned by the President to the White House residence. He regularly traveled with Trump, and was seen boarding Marine One on the South Lawn of the White House as Trump headed for Pennsylvania on Saturday.
He was scheduled to travel to California with Trump on Tuesday, but then he was fired.
McEntee, who joined the Trump campaign in its first months, is the latest of the President's longest-serving aides to leave or announce plans to leave the White House, following the resignation of White House communications direct Hope Hicks two weeks earlier.
McEntee served as Trump's body man during the campaign and into the White House alongside the President's longtime bodyguard Keith Schiller, who left the White House last fall. The role meant McEntee was nearly constantly at the President's side.
The Wall Street Journal first reported the news of his exit.
Trump reelection campaign manager Brad Parscale announced McEntee's hire alongside that of Katrina Pierson, a Trump campaign spokesperson in 2016 who will join the 2020 campaign as a senior adviser.
"As we build out our operations for the 2018 midterm elections and the 2020 reelection campaign, we are pleased to welcome back two outstanding members of our 2016 team," Parscale said in a statement. "We need the help of proven leaders such as Katrina and John to promote the President's growing portfolio of achievements across the country."
McEntee is just the latest aide to leave the White House amid issues with his security clearance, after White House chief of staff John Kelly enacted a series of reforms following the scandal involving disgraced White House staff secretary Rob Porter.
Kelly sought to limit access to classified information for aides with longstanding interim security clearances and several aides have since left the White House after it became clear their applications for a full security clearances would not be approved.