"In 1864, Territorial Governor John Evans appointed the Reverend John Chivington as Colonel of the Colorado Volunteers with orders to protect white settlers from the Cheyenne and Arapaho warriors who were accused of stealing cattle. Colonel Chivington ordered his men to attack a band of Cheyenne and Arapaho encamped along Sand Creek. Chivington reported that his troops killed more than 500 warriors. The militia returned to Denver City in triumph, but several officers reported that the so called battle was a blatant massacre of Indians at peace, that most of the dead were women and children, and that bodies of the dead had been hideously mutilated and desecrated. Three U. S. Army inquiries condemned the action, and incoming President Andrew Johnson asked Governor Evans for his resignation, but none of the perpetrators was ever punished. This event is now known as the Sand Creek Massacre"... Wikipedia
"Among the chiefs killed were most of those who had advocated peace with white settlers and the U.S. government. The net effect of the murders and ensuing weakening of the peace faction exacerbated the developing social and political rift. Traditional council chiefs, mature men who sought consensus and looked to the future of their people, and their followers, were opposed by the younger and more militaristic Dog Soldiers"... Wikipedia
These historical incidents remind us that the United States has done its share of crimes against humanity and that giving men guns and authorizing them to kill is always a dangerous game with unintended consequences.