First Lieutenant Mathis was the pilot of a F-51D Mustang night fighter with the 39th Fighter-Interceptor Squadron, 35th Fighter-Interceptor Group. On 10 August 1951, while on a combat mission in the Pyongyang area, his engine suffered coolant problems and the aircraft crashed northwest of Yongdok. His remains were recovered.

Mathis was awarded the Purple Heart, 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.