Good friend of - and former brother-in-law of - writer Norman Mailer , Knox was married to his second wife Adele''s sister.Met Norman Mailer in Hollywood in the late 1940s, the period that Mailer adapted for his novel "The Deer Park" (1954).Moved to Italy in the 1950s after he was blacklisted over his left-wing politics.Witnessed the suicide of bit-part actor Al Mulock n the set of the movie C'era una volta il West (1968) ("Once Upon a Time in the West"). Mulock committed suicide on by jumping from a hotel, on location in Guadix, Spain. Knox, who had been hired by director Sergio Leone as a screenwriter, was sitting in a hotel room with production manager Claudio Mancini and saw Mulock's body pass their window. Knox recalled in an interview that while Mancini put Mulock in his car to drive him to the hospital, Leone said to Mancini, "Get the costume! We need the costume!" Mulock, who had appeared as the one-armed bounty hunter in Leone's Il buono, il brutto, il cattivo. (1966), was wearing the costume he wore in the movie when he made his fatal leap.Woody Harrelson 's character in Natural Born Killers (1994) is named after Knox.Talks about appearing on stage with Lon Chaney Jr. in a production of "Of Mice and Men" in the book "A Sci-Fi Swarm and Horror Horde" (McFarland & Co., 2010) by Tom Weaver .