John Bolton's chief of staff out at National Security Council

Fred Fleitz, who joined the administration this summer, will soon return to the Center for Security Policy, the conservative think tank where he worked as vice president for policy prior to leaving for the NSC post.

"Fred Fleitz is a longtime friend and adviser. He's been a valuable member of the National Security Council team. I wish him the best with his next endeavor," Bolton said in a statement to CNN.

Fleitz will return as president and CEO of the Center for Security Policy starting in January 2019, according to the think tank. His first day back at the organization, however, will be November 1 -- one day after he officially leaves the White House, according to a senior administration official.

Critics have accused the Center for Security Policy of promoting anti-Muslim views.

Its controversial founder and current leader, Frank Gaffney, will transition into the role of executive chairman after Fleitz succeeds him, the group said on Monday.

The staff shake-up comes as the National Security Council grapples with the complicated issue of Saudi Arabia's suspected involvement in the alleged killing of a Saudi journalist and government critic earlier this month.

Bolton brought in several staffers after he became President Donald Trump's national security adviser in May. Fleitz, who also served as Bolton's chief during the Bush administration, is the first of Bolton's senior hires to leave the council.