I got this from "The American Holocaust: Columbus and the Conquest of the New World" by David Stannard, which heavily documents this, and many other atrocities done to the indigenous.
There archaeological evidence going back nearly a millennium prior to this.
One significant pre-Columbian example:
The Crow Creek site is a massive village on the Missouri River in south-central South Dakota. The Initial Coalescent component covers 7.3 ha (18 acres) and is enclosed by a large, bastioned fortification ditch. The size of the village and the presence of the ditch suggest intergroup hostilities. In 1978 excavations at the northwest end of the fortificaton ditch recovered the remains of at least 486 individuals dated toAD 1325. Analysis of the skeletal material indicates that men, women, and children were present. Many were scalped, decapitated, and dismembered, and there are other indications of violence. Chewing on many of the elements demonstrates that the remains were exposed above ground for some period before burial. The Crow Creek crania are metrically most similar to those from St. Helena and early Arikara sites, suggesting affinities with those groups. Crow Creek has important implications for understanding intergroup relations and warfare in the Missouri River trench during the thirteenth and fourteenth centuries.
https://www.tandfonline.com/doi/abs/10.1080/2052546.1993.11931655
Yes, various bands could be quite brutal towards their enemies, no doubt, and I could mention some of them if you're interested as I studied this in my anthropology studies, including spending much time on numerous reservations here and in the northern plains.
That sounds very interesting.
I don’t have a particularly wide knowledge of this area of history, but took a bit of an interest and have read a few things recently.
I was surprised how violent many tribes were, especially towards captured foes. Also quite how violent, on both sides, European expansion into the South/West were.
Also interesting that expansion was at times an imperial competition between groups, for example, Spanish and Comanche, with both groups trying to conquer and control new land. In this the Spanish were often the de facto vassals.
Strangely, at times, both groups were dependent on each other despite being enemies and would need to pause hostilities to trade. Or when they tried to form longer peaces then it had to be done based more on adapting to Comanche customs than getting them to adopt European ones. Then some local leader trying to explain to someone in Spain who is uninterested in understanding local realities, or a clueless new official arriving determined to show the 'heathens' who is boss, usually with disastrous consequences.
The Comanche Empire by Pekka Hämäläinen is a good book about it.
While it doesn't really show the most positive aspects of human nature, the clash and interaction of cultures is certainly interesting history.