John I. Turnbull ("Jack") was the younger brother to Douglas of lacrosse fame. He, like his brother, was a graduate in engineering from The Johns Hopkins University. While at Hopkins, he was selected to be First Team All America in lacrosse for three consecutive years. He was captain of the American Olympic Lacrosse Team (1932) and played also on the 1936 lacrosse team (both won the Olympic competition) and was also on the American Field Hockey Team in 1936. He enlisted in the U.S. Army Air Corps and, as co-pilot of a B-25, was shot down and died three days later in northern France, in 1944, having attained the rank of Lt. Col. Jack never married.