Sergeant Gregg was a member of Company K, 3rd Battalion, 9th Infantry Regiment, 2nd Infantry Division. He was taken Prisoner of War while fighting the enemy in North Korea on 26 November 1950 and died while a prisoner on 28 February 1951. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Sergeant Gregg was awarded the Combat Infantryman Badge, the Prisoner of War Medal, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.