Gary Mack Remembering Gary Mack, JFK Assassination Conspiracy Theorist Turned Historian By Courtney Collins • Jul 16, 2015 Youtube Dallas has lost its leading expert on the Kennedy assassination. The longtime curator of the Sixth Floor Museum, Gary Mack, died Wednesday at the age of 68. Friends say he suffered from an aggressive cancer. Gary Mack, Sixth Floor Museum Curator And JFK Expert, Dies At 68 By Eric Aasen & Krystina Martinez • Jul 15, 2015 David Woo / The Dallas Morning News file photo Gary Mack, the longtime curator of the Sixth Floor Museum and an expert on the President Kennedy assassination, died this morning. He was 68.