Captain Cooney was a veteran of World War II. In Korea, he was a the commanding officer of Company G, 3rd Battalion, 7th Marines, 1st Marine Division. He was killed by a sniper while checking to ensure none of his men were left behind during withdrawal from Hill 1425 near Yudam-ni, North Korea on November 27, 1950. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.