I don't know if you are aware of this or not, but Billy Chapman was in reality Nelson Knight Chapman, who the 1860 census shows as a Kentucky-born, 23-year-old cooper or barrel maker living with the William Chapman family in west Moniteau County. I am sad to say I don't remember who clued me into this but it led me to the 1883 Henry County history that provided a bit of bio for the man. Maybe it was hrf who told me where to look. This seems to show N. K. Chapman was a southern recruiter working in the Morgan County area and the man who wrote that 1 November 1864 St. Louis "Daily Missouri Democrat" newspaper article was taking liberties with just how bloodthirsty Chapman was supposed to be. The Henry County history says that Chapman was arrested in Greene County Missouri (Springfield area) as a spy, tried and convicted by a military tribunal, but escaped and came to his home region around Syracuse and Tipton. It says he moved to Windsor, northeast Henry County in 1871, opened a wagon shop, later became an attorney (1878), and city attorney (1883).
I draw a blank on Puckett who supposedly was Chapman's right-hand man. This makes me wonder if the newspaper correspondent mangled the name so badly that even an alphbetical check in the 1860 census index fails to show the right name. If he got the first letter wrong, that could easily be the case. It's sad that such a small error can throw research and genealogy off track, but I have seen this happen with the most innocent sounding errors.