President Donald Trump fired his longtime personal assistant, John McEntee, on Monday.

CNN cited a source as saying McEntee is the subject of a financial-crimes investigation by the Department of Homeland Security.

McEntee was escorted from the White House on Monday, The Wall Street Journal reported.

Trump's reelection campaign hired McEntee soon after his firing.

President Donald Trump's longtime personal assistant, John McEntee, was fired from his White House position on Monday.

CNN cited a source as saying McEntee is the subject of a financial-crimes investigation by the Department of Homeland Security. The Wall Street Journal reported that the reason for his firing was "an unspecified security issue."

McEntee was escorted out of the White House on Monday without being allowed to collect his belongings, including his jacket, The Journal reported, citing White House officials.

McEntee joined the president's small team three years ago during the earliest days of Trump's presidential campaign.

"It's not going to be great for morale," a White House official told The Journal about McEntee's firing.

Soon after, Trump's 2020 reelection campaign released a statement announcing that McEntee would join its ranks as a "senior advisor for campaign operations" along with Katrina Pierson.

"As we build out our operations for the 2018 mid-term elections and the 2020 reelection campaign, we are pleased to welcome back two outstanding members of our 2016 team," said Brad Parscale, the campaign manager. "We need the help of proven leaders such as Katrina and John to promote the President's growing portfolio of achievements across the country."