CIA Director Allen Dulles was fired by JFK after Bay of Pigs fiasco, yet served (prominently) on the Warren Commission to "investigate" the assassination.

From: http://www.jfkmurdersolved.com/bush.htm

Allen Dulles, later CIA director, was the architect - together with Vice President Richard Nixon and George Bush - of the Bay of Pigs invasion to overthrow Fidel Castro's Cuba. Allen Dulles was fired by President Kennedy because of the fiasco of the Bay of Pigs. Yet Allen Dulles was appointed by Lyndon Johnson to serve on the Warren Commission to "investigate" JFK's death.