Private Kellner was a member of Company I, 3rd Battalion, 8th Cavalry Regiment, 1st Cavalry Division. On 29 January 1951, he was riding in a truck that rolled down a cliff five miles north of Chunju, South Korea, killing him.

Kellner was awarded the Combat Infantryman Badge, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal and the Korean War Service Medal.