Corporal Mehlhorn was a member of Company B, 1st Battalion, 1st Marines, 1st Marine Division. He was Killed in Action while fighting the enemy in Korea on 7 July 1951.

Mehlhorn was awarded the Purple Heart, the Combat Action Ribbon, 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.