I just found this
COMBS, BOLIVAR C.: b. 5/7/1831. Farmer. Enl. 4/21/61 in Co. A. Promoted to Cpl. ca. May 1862. Died in camp "unexpectedly of apoplexy" on 8/14/62.
Apoplexy was an old term for stroke but by this term an old time physician could have meant any number of things.. So it seems that Mr. Combs died of natural causes.