In 1864, the U.S. military told a group of Cheyenne and Arapahoe peoples that they could settle in Colorado and promised to protect them from attack. However, on November 29, U.S. soldiers surrounded the camp, which consisted mostly of women and children. Most of the camp's men were on a hunting expedition. John Smith, a local Indian agent who witnessed the event, estimated the soldiers numbered 800 to 1,000. Some of the officers told the officer in command, Colonel John Chivington, that the Native Americans had been promised protection. Even so, Chivington ordered his soldiers to open fire, killing between 150 and 500 Native Americans.
Which event is this?