Here is the biography of Horace McMahon:
Born on May 17, 1906, in Connecticut, Horace McMahon was a character actor who played both sides of the legal fence in over a hundred films. He discovered acting while pursuing a law degree at Fordham University, and his early career was marked by playing various hoods, thugs, jailbirds, mobsters, and murderers in crime yarns.
Before breaking into acting, McMahon worked as a shipping clerk, mail deliverer, and news reporter for The South Norwalk Sentinel. He made his Broadway debut in 1931 and went on to play in numerous New York shows, including "Wonder Boy," "Wild Waves," "Man Bites Dog," "Knock on Wood," "Three Men on a Horse," and "Red Gloves."
McMahon's distinctive look and cynical attitude made him a natural fit for playing tough, streetwise characters, and he appeared in a slew of unbilled movie bits in the late 1930s and 1940s. He often played characters with typical street-tough names like "Fingers," "Limpy," "Brains," "Maxey," "Swifty," and "Looey."
In the 1940s, McMahon began to transition to playing good-guy cops and detectives, and his most famous role was as New York City Lt. Monaghan in the Broadway play "Detective Story." He reprised the role in the 1951 film adaptation, which was nominated for four Oscars.
McMahon continued to work in film and television throughout the 1950s and 1960s, appearing in a wide range of roles, including episodes of "Martin Kane," "Lux Video Theatre," "The Lone Wolf," "Climax!," The Ford Television Theatre," "Undercurrent," and "Suspicion." He received an Emmy nomination for his regular role as Lt. Mike Parker on the TV series "Naked City" and had a regular role on the series "Mr. Broadway."
McMahon's final on-camera appearance was on the TV shows "My Three Sons" and "Family Affair." He was married to actress Louise Campbell for many years and had three children. He died of a heart ailment on August 17, 1971, at the age of 65.