"In 1889 when but 19 years of age, Mattox was a member of the police force of South Oklahoma City, when a dispute arose over the city marshalship. John Hayward, the town marshal, had refused to surrender the office to the marshal-elect. The latter employed Mattox to gain possession of the office and Mattox carried the day by shooting and killing Hayward. He was acquitted, however, on a plea of self-defense."