JFK was murdered for many reasons. Most pressing was likely the UFO issue, for he wanted to expose the black ops reverse engineering programs. He sent out two memos, one unclassified and another classified, ten days before his death basically telling NASA/AF to share all their files on the subject.
In addition to the Confidential National Security Action Memorandum, Kennedy issued a more highly classified “Top Secret” Memorandum to the Director of the CIA.
Dated the same day of November 12, 1963 the subject header of the file was:
“Classification review of all UFO intelligence files affecting National Security.”
The Top Secret Memorandum went on to say:
[I] have instructed James Webb to develop a program with the Soviet Union in Joint space and lunar explorations. It would be very helpful if you would have the high threat [UFO] cases reviewed with the purpose of identification of bona fides as opposed to classified CIA and USAF sources…. When this data has been sorted out, I would like you to arrange a program of data sharing with NASA where Unknowns [UFOs] are a factor. This will help NASA mission directors in their defensive responsibilities. I would like an interim report on the data review no later than February 1, 1964.