Jim Garrison was part of the coverup no less than Arlen Spector who managed the investigation who according to Mary Moorman, whose iconic Polaroid Photograph shows shooters including E Howard Hunt and Dallas Cop Joe Smith, and spectators including Martin Luther & Coretta King and Andy Warhol on the Grassy Knoll, who witnessed the Secret Service driver William Greer shoot President Kennedy from the front seat of the limo, changed the subject and adjourned for coffee breaks whenever she went to present hard evidence and FBI Head J Edgar Hoover. The Assassination of John F Kennedy.