Anyone interested in SAND CREEK should read MASSACRES OF THE MOUNTAINS by Dunn. Those Indians were not the sweet little natives portrayed in film.
Among the items found at the site were fresh scalps of white men and boys, a blanket fringed with the hair of white women.
In the camp, and captured, was George Bent, a Confederate agent believed to be instrumental in stirring up the tribes against the North as the Civil War was still raging.
Standard procedure for the Indians was to make war against the whites, then make peace in the fall, live on government rations, then in the spring go on the warpath again when the grass was tall enough to support a war pony. (From THE INDIAN WAR OF 1864 by Ware)
I linked to The National Park Service website.
The Treaty of the Little Arkansas in October 1865 acknowledged U. S. blame for the massacre, but it also extinguished Cheyenne and Arapaho rights to land titles in Colorado.
Interesting how much of the truth of history is rewritten to suit a political agenda.