JFK wrote to in a letter to Mary Pinchot Meyer in October 1963 — a letter he never sent. JFK was shot to death the next month. And the following year, Meyer too was shot to death.
From the Wikipedia page for Mary Pinchot Meyer:
In 1983, former Harvard University psychology lecturer Timothy Leary claimed that in the spring of 1962, Pinchot Meyer, who, according to her biographer Nina Burleigh "wore manners and charm like a second skin", told Leary she was taking part in a plan to avert worldwide nuclear war by convincing powerful male members of the Washington establishment to take mind-altering drugs, which would presumably lead them to conclude that the Cold War was meaningless.
According to Leary, Meyer had sought him out for the purpose of learning how to conduct LSD sessions with these powerful men, including, she strongly implied, President John F. Kennedy, who was then her lover. Leary alleged that Pinchot Meyer told him she had shared in this plan with at least seven other Washington socialite friends who held similar political views and were trying to supply LSD to a small circle of high-ranking government officials. Leary also claimed that Pinchot Meyer had asked him for help while in a state of fear for her own life after the assassination of President Kennedy.
In his biography Flashbacks (1983), Leary claimed he had a call from Pinchot Meyer soon after the Kennedy assassination during which she sobbed and said, "They couldn't control him any more. He was changing too fast...They've covered everything up. I gotta come see you. I'm afraid. Be careful."...