Presidency of John F. Kennedy killed Oswald due to his own grief over Kennedy's death, but the assassination of Kennedy and the death of Oswald gave rise to enormous speculation that Kennedy had been the victim of a conspiracy. Kennedy was succeeded as president by Lyndon Johnson, who stated on November 27 that "no memorial or oration or eulogy could more eloquently honor President Kennedy's memory than the earliest possible passage of a civil rights bill for which he fought so long." President Johnson created the Warren Commission—chaired by Chief Justice Earl Warren—to investigate the assassination. The Warren Commission concluded that Oswald acted alone in
John F. Kennedy assassination conspiracy theories Kennedy and others. Historian Michael L. Kurtz wrote that there is no evidence suggesting that Johnson ordered the assassination of Kennedy. According to Kurtz, Johnson believed Fidel Castro was responsible for the assassination and that Johnson covered up the truth because he feared the possibility that retaliatory measures against Cuba might escalate to nuclear war with the Soviet Union. In 2012, biographer Robert Caro published his fourth volume on Johnson's career, "The Passage of Power", which chronicles Johnson's communications and actions as Vice President, and describes the events leading up to the assassination. Caro wrote that "nothing that I have