It's not what you were looking for, but I did find a link to a short newspaper article about his death:
https://www.newspapers.com/clip/88851935/
as well as the FindaGrave site that lists the news article:
https://www.findagrave.com/memorial/104310568/charles-c.-austin
I am also skeptical that he is son of John and Mariah, who looks to have been in Maine as late as the 1860 Census and 1863, when he has a draft registration record. Your Charles was enlisted in a Wisconsin regiment in1864, which seems out of whack with the Charles in York, Maine.
I also note that the 1870 U.S. Census has a C.C. Austin with a son Gilbert born ca. 1860 in Wisconsin.
https://www.ancestry.com/discoveryui-content/view/5741927:7163
The timing does not seem to work for the other Charles in York, Maine.