He died on February 21, 1865 of Pnenumonia. My records show that he was with the Unassigned Conscripts. The GD on his tombstone I am assuming means Guards. I do see this on one page of his CMSR's. (Compiled Military Service Records)
He was captured on December 14, 1864 at Bristol, TN. He was taken to Louisville, KY., and from there transferred to the Camp Chase Prison where he arrived on January 15, 1865.
According to the Camp Chase records it was manatory that the Confederate prisoners were to answer roll call every morning. This means that the prisoners would stand in groups outside and be counted. How long it took depended upon how many prisoners had to be counted. Camp Chase was near full capacity when he arrived. The penalty for not showing up was NO food for that day for that soldier. Many of the prisoners had little or NO shoes. Just a couple of days of his arrival at Camp Chase the temperature at Camp Chase went down to 19 degrees below zero according to the Ohio State Journal (Columbus, Ohio Newspaper) and that is of course without the wind chill factor. Needless to say a lot of prisoners went without a handful of food. Another factor that may have led to his death was the news of Andersonville where Union prisoners were dying at a alarming rate. Almost 50% of the deaths at Camp Chase occured in 1865 and 25% of all Camp Chase deaths occured in February of 1865. Your ancestor fit into this catagory. 498 Confederates died in February 1865 at Camp Chase. Camp Chase was a prison camp from 1861-1865 between 2000 and 2100 Confederates would die there. Andersonville was only open for about one year (1864) and almost 13,000 would die there.
According so some prisoners who made it through Camp Chase, they remembered moaning and pleas for help and crying during the nights. Those testimonies were made in 1863 when conditions were not as harsh as 1865. Although the barracks did have stoves, they were not allowed to be used at night, only during the day. One blanket per prisoner was issued. Because of an attempted escape in July on 1864 food was again reduced. The thought process was that an under fed prisoner would be less likely to make an escape. In many respects Camp Chase in 1865 was worst than Valley Forge during the American Revolution.
Very little is known about the Unassigned Conscripts. Another Confederate soldier named Isaac M. Arrants was also with that unit. He too would die at Camp Chase. I am doing bio's on all of the Confederate dead at Camp Chase. I have not yet done John Brown's bio as the Unassigned Conscripts will take a lot of time. My gut feeling is that the only thing he had in common with Bristol, TN was that it was his capture site. He had such a common name and rare unit that he will take additional time. I also suspect that other John Brown's are mixed in with his CMSR's. One of reasons why I suggest this was because it shows a Jno Brown as being a courier for the Unassigned Conscripts but he was marked as present with General Johnston and his surrender to General Sherman in North Carolina. There are mistakes in the CMSR's and I'm not sure at this time how to understand them. Since you are looking into his genealogy I will ask you if he had ever lived in Augusta County South Carolina? This may answer some questions. Also do you show any ties to him living in Alabama?
I will leave you may email address and when you contact me I will forward your email to a woman who also had an ancestor in the Unassigned Conscripts who died at Chase. She has been doing some additional research on her ancestor and perhaps she might be able to shed some additional information. This site that you're on does offer his CMSR's should you decide to order them. dennis_brooke2001@yahoo.com