The acting head of the Drug Enforcement Administration (DEA) will step down at the end of this month, Fox News confirmed Tuesday.

Chuck Rosenberg will leave his position effective Oct. 1, a DEA source told Fox. A reason for his departure was not given.

Rosenberg's resignation was first reported by The New York Times, which claimed that he was "disillusioned" with President Donald Trump.

According to the paper, Rosenberg is a close confidant of former FBI Director James Comey, whose dismissal by Trump in May is the focal point of an ongoing investigation into alleged collaboration between Trump's campaign and Russian officials.

The Times also reported that Rosenberg sent an email to all DEA employees decrying comments Trump made in July about police treatment of suspects.

"When you see these thugs being thrown into the back of a paddy wagon — you just see them thrown in, rough," Trump told an audience of law enforcement officers in Suffolk County, N.Y., "I said, 'Please don't be too nice.'"

"We must earn and keep the public trust and continue to hold ourselves to the very highest standards," Rosenberg wrote at the time. "Ours is an honorable profession and, so, we will always act honorably."

Fox News' Jake Gibson contributed to this report.