Greetings!
I read it in a book entirely about the Cherokee culture, as I, being part Cherokee, have always been very interested in.

The book was written by a good scholar, and the book discussed in detail the every aspect of Cherokee culture. It was very interesting.

Sadly, I don't remember the name of it, but I do plan on adding it to my collection.
In addition, as I recall, the Cherokee warriors didn't stop to do this while in the midst of battle, but they usually did so in victory celebrations at night afterwards. In reading numerous books on Cherokee culture, as well as that of the Iroquois, it seems to be consistent with the culture of the Eastern Tribes in my opinion. The Indian tribes of the east needed no such instruction in cruelty or ferocity by the white man, and were peerless warriors and highly skilled in all manner of irregular warfare, including deploying all manner of ruses and deceptions, as well as terror and other forms of psychological warfare.
In my other readings, it has come to my attention that unlike most people's exposure to the Indian Wars, where it takes place post-Civil War, there was in fact a long process of ferocious warfare between the Indians and the white invaders virtually from the beginning--in the mid-1600's, all the way to the closing chapters of native resistance in the 1890's. Some four-hundred years of desperate warfare, fought through dozens, hundreds of tribes, through the length and breadth of the continental United States, through all seasons and all climates.
Interestingly, in the first two centuries of warfare, the eastern tribes, usually being larger, more organized, and culturally somewhat more developed and sophisticated, regularly fielded fighting formations numbering in the thousands, whereas in the later struggles in the west, a few hundred at a time seemed to be the norm. There are numerous accounts of formations of one, two, three thousand or more of Indian warriors gathering to fight white armies in the east, with horrific pitched battles through the dark forests. In some of these battles, the Indians actually won, with hundreds and even thousands of white casualties. It stands in stark contrast to the rather small battles, and considerably smaller casualties sustained in battles throughout the west.
Still, despite some impressive achievements through the forest battlefields in the East, the same overall lack of political unity allowed the white colonies to increasingly gain the upper hand, both in raw numbers, and in the leveraging of superior technology.
I hope this is interesting!
Semper Fidelis,
SHARK