Is Donald Trump about to lose another close aide?

White House sources have told CNN that Keith Schiller, the director of Oval Office operations, intends to resign. The sources say his departure will take place in late September or early October.

Schiller's reason for wanting to leave his high-level White House post is allegedly financial. His current salary is $165,000 annually, significantly less than the $294,000 he made before as an employee with the Trump Organization and the Trump campaign, and from his private security firm, according to White House financial disclosures.

However, one of the sources said Schiller has been frustrated by White House chief of staff John Kelly. Kelly has restricted access to the president since joining the administration, and Schiller has reportedly complained that he has to call the White House switchboard just to speak to the president on the phone.

You may remember Schiller as the man who Trump sent to fire James Comey. Schiller delivered the letter to FBI headquarters that notified the former FBI director of his termination.

Few people are closer to Trump than Schiller. Schiller has worked with Trump for almost 20 years, starting as a part-time bodyguard in 1999, and is one of the few carryovers from Trump's business mogul days. He's a former NYPD detective who has served as a bodyguard and personal aide both during the campaign through the presidency.