Why were the American Indian so brutal to each other?

The first ''war'' the colonist fought with the Indians was to wipe out an other tribe We know they just kidnapped women to fill their needs. During the beaver wars the Iraqis just killed any one that came on their hunting grounds which included the whole state of Ohio The Iraqis don't not live there just hunted beaver to trade for British rum and guns it was not until they wiped out the beaver population in these states that the wars stopped These are some who feel they can prove the north American Indian also engaged in cannibalism So why were they so barbaric?