 The scene where Tom shoots the horse that threw and killed Sam  "Nails" Nathan in a riding accident was based on an actual incident.  In 1924, Sam "Nails" Morton, a member of Dion OBanions gang, was  thrown from his horse and killed while riding in Chicagos Lincoln  Park. Other members of the gang, led by Louis "Two Gun" Alteri,  kidnapped the horse, took it to the spot where the accident  occurred, and shot it dead. Source: Carl Sifakis, "Encyclopedia Of  American Crime."