Some background and quotes pertaining to the Sand Creek Massacre
(from eyewitnesses and other sources)

The stage had already been set for a potential massacre. In what was an election year with many pushing for statehood, the papers and others were busy stirring up resentment and even hatred for the Indians (The Rocky Mountain News being a chief instigator). At the time, a rival newspaper claimed that it was due to aspirations of political gain and the desire for statehood and that some of the stories were designed to prey on settler fears about the Indians. They went on to say that The News was trying to prove to the voters "that only as a state could Colorado get sufficient troops to control her Indians." As the year progressed, just about any rumor was presented as fact and any time there was violence between whites and Indians, it was called a "massacre."

As there were some acts of violence between the groups, it was just enough "truth" (combined with propaganda) to enable such statements as that of The News in August 1864, where it called for settlers and the military to "go for them, their lodges, squaws and all."

After a family was killed (not that it was known which group of Indians was even responsible), the Governor and his allies finally had their "justification." When he issued the proclamation to have citizens form into regiments of soldiers (who were essentially given the green light to kill any Indian with impunity), he followed it with another stating that most of the Indians were "hostile" and that they military had the duty to "pursue, kill, and destroy them all."

Sometimes called The Chivington Massacre, after Colonel John M. Chivington. Chivington, who was not only a former Methodist missionary (and still an elder) but also a candidate for Congress that year, was highly in favor of "extermination." In a speech, he gave his policy as to "kill and scalp all, little and big." And while he wasn't the originator of the phrase, he was very fond of " Nits make lice," meaning that any survivors (up to and including women and children) would only defeat the purpose of the extermination. (A frightening parallel can be found in Heinrich Himmler's description of the Nazi genocide as being "the same as delousing.")

Witnesses reported that when he had been informed that the Indians at the site were considered harmless, he dismissed it saying "Well, I long to be wading in gore." It was also reported that following the massacre, some members of Congress had confronted Chivington and the Governor, before members of the public at the Denver Opera House. At one point it was asked whether it would be better to civilize or exterminate the Indians. In a letter from one of the senators to a friend, he wrote that "there suddenly arose such a shout as is never heard unless upon some battlefield—a shout almost loud enough to raise the roof of the opera house—'EXTERMINATE THEM! EXTERMINATE THEM!'"

The News referred to the massacre as "The Battle of Sand Creek." This being despite the fact that the Indians, having been giving some assurance that if peaceful they would be protected, most of the adult braves were out hunting, and that the Indians had relinquished their firearms except those needed for hunting. As one of Chivington's guides said, of the 600 or so in the camp at the time of the attack, there were about "thirty-five braves and some old men, about sixty in all" (the remainder being women and children). Chivington had 700 armed soldiers and artillery.

In his testimony he claimed his intelligence had told him there were some 1100-1200 Indians, of which 700 were " warriors." While admitting knowledge that there were women and children, he also claimed no knowledge of "old men among them" (later in the testimony, he said that following the massacre he saw few women and children among the slain). He also said that "there was an unusual number of males among them, for the reason that the war chiefs of both nations were assembled there evidently for some special purpose." Something that isn't corroborated by other testimony.

The News also made mention that "the Indian camp was well supplied with defensive works. For half a mile along the creek there was an almost continuous chain of rifle-pits, and another similar line of works crowned the adjacent bluff. Pits had been dug at all the salient points for miles." Neglecting that there were no Indians manning them with rifles. Or that the Indians were attacked under both the American and white flags. It also referred to the Sand Creek encampment as "one of the most powerful villages in the Cheyenne nation." That "Cheyenne scalps are as thick here now as toads in Egypt" and that "everybody has got one and is anxious to get another to send east."

It ended an editorial on the subject with:

A thousand incidents of individual daring and the passing events of the day might be told, but space forbids. We leave the task for eye-witnesses to chronicle. All acquitted themselves well, and Colorado soldiers have again covered themselves with glory.
While the massacre was a source of outrage among many people, despite an investigation by Congress, no real severe penalty was handed out to anyone involved.

(Sources: some quotes from The Rocky Mountain News and Chivington's testimony come from; the rest, including those below are from David E. Stannard's 1992 American Holocaust: Columbus and the conquest of the New World)

(The following quotes are graphic eyewitness testimony from the massacre. It begins as chilling and eventually becomes almost numbing, but seems the only way to begin to appreciate the horror of the incident. I won't distract from the text with links or commentary, it speaks for itself.)

After the firing the warriors put the squaws and children together, and surrounded them to protect them. I saw five squaws under a bank for shelter. When troops came up to them they ran out and showed their persons, to let the soldiers know they were squaws and begged for mercy, but the soldiers shot them all.... There were some thirty or forty squaws collected in a hole for protection; they sent out a little girl about six years old with a white flag on a stick; she had not proceeded but a few steps when she was shot and killed. All the squaws in that hole were afterwards killed, and four or five bucks outside. The squaws offered no resistance. Every one I saw dead was scalped. I saw one squaw cut open with an unborn child, as I thought, lying by her side. Captain Soule afterwards told me that such was the fact.... I saw quite a number of infants in arms killed with their mothers.
Robert Bent, guide

I went over the ground soon after the battle. I should judge there were between 400 and 500 Indians killed.... Nearly all, men, women, and children were scalped. I saw one woman whose privates had been mutilated.
Asbury Bird, Company D of the First Colorado Cavalry

The bodies were horribly cut up, skulls broken in a good many; I judge they were broken in after they were killed, as they were shot besides. I do not think I saw any but what was scalped; saw fingers cut off [to take rings] saw several bodies with privates cut off, women as well as men.
Sergeant Lucien Palmer, First Cavalry's Company C

Next morning after the battle, I saw a little boy covered up among the Indians in a trench, still alive. I saw a major in the 3rd regiment take out his pistol and blow off the top of his head. I saw men unjointing fingers to get rings off, and cutting off ears to get silver ornaments. I saw a party with the same major take up bodies that had been buried in the night to scalp them and take off ornaments. I saw a squaw with her head smashed in before she was killed. Next morning, after they were dead and stiff, these men pulled out the bodies of the squaws and pulled them open in an indecent manner. I heard men say they had cut out privates, but did not see it myself.
Corporal Amos C. Miksch, Company C

I saw some Indians that had been scalped, and the ears were cut off of the body of White Antelope. One Indian who had been scalped had also his skull all smashed in, and I heard that the privates of White Antelope had been cut off to make a tobacco bag out of. I heard some men say that the privates of one of the squaws had been cut out and put on a stick.
Captain L. Wilson, First Colorado Cavalry

The dead bodies of women and children were afterwards mutilated in the most horrible manner. I saw only eight. I could not stand it; they were cut up too much...they were scalped and cut up in an awful manner.... White Antelope's nose, ears, and privates were cut off.
Private David Louderback, First Cavalry

All manner of depredations were inflicted on their persons, they were scalped, their brains knocked out; the men used their knives, ripped open women, clubbed little children, knocked them in the head with their guns, beat their brains out, mutilated their bodies in every sense of the word...worse mutilated than any I ever saw before, the women all cut to pieces.... [C]hildren two or three months old; all ages lying there, from sucking infants up to warriors.
John S. Smith, interpreter

In going over the battle-ground the next day I did not see a body of a man, woman, or child but was scalped, and in many instances their bodies were mutilated in the most horrible manner—men, women, and children's privates cut out, &c. I heard one man say he had cut out a woman's private parts and had them for exhibition on a stick; I heard another man say that he had cut the fingers off an Indian to get rings off his hand.... I also heard of numerous instances in which men had cut out the private parts of females and stretched them over the saddle-bows, and wore them over their hats while riding in the ranks.... I heard one man say he had cut a squaw's heart out, and had stuck it on a stick.
First Lieutenant James D. Cannon, New Mexico Volunteers

One last quote, not from a participant:

"[The Sand Creek Massacre was] as righteous and beneficial a deed as ever took place on the frontier."
Theodore Roosevelt