1931. Retirement from boxing and movie career Callahan retired from professional boxing around 1932. Though he could take a punch, his decline might be explained by the abdominal injuries he received in his 1927 bout with Baker and from which he never fully recovered. Callahan also suffered injuries to his hands early in his career that contributed to his retirement. Shortly after his last fight, Callahan began to referee boxing matches, working more than 400 matches between December 1932 until November 1960. He stayed close to the Los Angeles area as a referee, so he could pursue his career in the movie industry during this period. After gaining a decade of experience as a referee, Callahan simultaneously worked as a boxing judge for over 100 fights mostly in the Los Angeles area, including four state championships, between 1941 and 1960. On October 9, 1937, Callahan was scheduled to box in a benefit exhibition at Legion Stadium in Los Angeles for Wad Wadheim, a fight promoter who had suffered a stroke. Among the 50 or so boxers to participated were triple World Champion Henry Armstrong, Callahan's opponents Jackie Fields, Ace Hudkins, and Jack Silver, as well as Young Jack Thompson, Abe "The Newsboy" Hollandersky, Fidel La Barba, ex-Middleweight champion Al McCoy, Jim Jeffries, and Maxie Rosenbloom. As a fighter, Callahan had met Jack Warner of Warner Bros. and complained to him about the quality of on-screen boxing and made suggestions about how to make it more authentic looking. Warner suggested Callahan come work for him once he retired from boxing. In 1933, Callahan took Warner up on the offer, and he was placed in charge of the Warner Bros. prop department. He soon was tapped by studios to choreograph boxing scenes, including the original 1937 and Elvis's 1962 remake of Kid Galahad and the 1938 sequel The Kid Comes Back, and to train and condition actors. He served as technical adviser on a number of films, include Warner's 1942 Gentleman Jim in which he also did fight choreography, Warner's 1948 Whiplash, Columbia Pictures' 1948 Leather Gloves, and Ventura Pictures' 1957 The Crooked Circle. He also appeared in bit parts in at least a dozen films, most commonly as a referee. As a stuntman on Paramount's 1953 War of the Worlds, Callahan suffered burns while performing one of the first full-body fire stunts on film. Among the actors he trained were Montgomery