What Made the 1864 Sand Creek Massacre in Colorado So

What made the 1864 Sand Creek Massacre in Colorado so atrocious?

A) Most of the victims were defenseless Cheyenne women and children whose bodies were scalped and mutilated.
B) Federal agents intentionally gave the Cheyenne tribe blankets infected with smallpox, which led to many deaths in a short amount of time.
C) Over 800 Cheyenne men were gunned down while they were hunting buffalo.
D) Colonel John M. Chivington's entire military force was ambushed and killed by Cheyenne warriors.