Darron,

September, 1861 was a time for battle deaths as well as deaths from disease. Even though it was relativley early in the war, deaths still occurred. You do not give the ancestor's name, unit, or locale of service. These 3 factors will figure into the equation. A unit's location in September, 1861 will tell you if they were involved in any action with the enemy. So, without knowing the previously mentioned 3 items, it is difficult to say and would only be a wild speculation.

Len