Here we have the event occurring September 15!

The Legion would become infamous due to their actions on September 15, 1862.[7] While trying to stop a Union advance through Baptist Gap, a popular leader among the Cherokee, Astoogahtogeh, was killed leading a charge. Enraged, the remaining Cherokee were driven to avenge him. In retaliation for Astoogahtogeh's death, the Cherokee scalped the dead Union soldiers after the battle. After the event was reported in newspapers, Union soldiers would fear the Cherokee, but Thomas feared for the reputation of the Cherokee, as he did not want his people to be seen as barbaric. The scalps were sent to be buried with the soldiers they originally came from.[6]

https://en.wikipedia.org/wiki/Cherokee_in_the_American_Civil_War#cite_ref-Rozema_6-1