Born in Redondo Beach, California 2nd Lt Heintzelman earned a bachelors of Science in Forestry in 1940 through Oregon State College. He was called to into service in Aug 1941. While on duty with General Douglas MacArthur’s troops serving with the 301 Field Artillery Regiment he was killed in the Philippines. 2nd Lt Heintzelman was survived by his parents.
https://www.findagrave.com/memorial/56755847
https://www.abmc.gov/node/358052
https://oregondigital.org/catalog/oregondigital:fx71bk75g#page/13/mode/1... (pg 13)
https://oregondigital.org/catalog/oregondigital:fx71b9585#page/16/mode/1... (pg 14)
https://www.dpaa.mil/portals/85/Documents/WWIIAccounting/california.html
https://oregondigital.org/catalog/oregondigital:fx71b9631#page/5/mode/1u... (pg 5)