Cook began shooting in 1939 while attending a Boy Scout Camp. In 1941 he came in last place in a Boy Scout team shooting match. He stayed with the sport and kept practicing. He won his first victory in 1946 at the National Junior Smallbore Rifle Championship. He then entered the University of Maryland and led them to the National Intercollegiate Team Championships in 1947 and 1949 where they set record scores both years. The team lost a close championship contest to the U.S. Naval Academy in 1948 and took second place. He was named to the All-American Rifle Team all three years. He left school in 1949 to work for a gun supply business.
In 1951, he joined the U.S. Air Force[2] He became a lieutenant and was assigned to the Gunnery Officers School.