First Lieutenant Harker was the pilot of a F-84D Thunderjet fighter with the 311th Fighter-Bomber Squadron, 58th Fighter-Bomber Group. On May 3, 1953, while on a night intruder mission between Sinanju and Nansi-dong, his aircraft disappeared from the radar screen. He was listed as Missing in Action and was presumed dead on May 4, 1954. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.