Friedman was returning from a speaking engagement in Columbus, Ohio, when he died suddenly at the Toronto Pearson Airport on Monday night, according to his family. He was 84. A nuclear physicist by training, Friedman had devoted his life to researching and investigating UFOs since the late 1960s. He was credited with bringing the 1947 Roswell Incident — the famous incident that gave rise to theories about UFOs and a U.S. military coverup — back into the mainstream conversation.