Angelina County was an anomaly at the time of the WBTS. The majority of its citizens did not favor secession and with all the hardships of war, the soldiers who enlisted, or were conscripted in 1862 may very well have been more conflicted than most other Texans. Your ancestor could have "died as a result of the civil war" for a variety of reasons. Perhaps he died after the War.

The last line of the following excerpt is flawed. The 13th Texas(Dismounted)Cavalry (your ancestor's original unit) was a component of Walkers Division and fought valiantly in many Louisiana skirmishes and then the Red River Campaign and Jenkins Ferry. Co. F was organized in Homer, Angelina County, Texas.

From the Handbook of Texas:

In 1861 Angelina County was the only county in East Texas, and one of only a handful of other Texas counties, to reject secession. This election result was startling when compared with that of Angelina County's neighbor to the immediate south, Tyler County, which supported secession by a 99 percent vote. Angelina County had also given the Constitutional Union party candidate, John Bell, a strong minority vote in the 1860 election. Two companies of county men were organized to fight in the Civil War, but they saw only limited action; only nineteen Angelina County men lost their lives in the war, and no Union soldiers entered the county before 1866.