The rest of the 7th Cavalry Regiment arrived led by Colonel James Forsyth and surrounded the encampment supported by four Hotchkiss guns.
On the morning of December 29, the troops went into the camp to disarm the Lakota. One version of events claims that during the process of disarming the Lakota, a deaf tribesman named Black Coyote was reluctant to give up his rifle claiming he had paid a lot for it. A scuffle over Black Coyote's rifle escalated and a shot was fired which resulted in the 7th Cavalry opening firing indiscriminately from all sides, killing men, women, and children, as well as some of their own fellow troopers. Those few Lakota warriors who still had weapons began shooting back at the attacking troopers, who quickly suppressed the Lakota fire. The surviving Lakota fled, but U.S. cavalrymen pursued and killed many who were unarmed.
By the time it was over, at least 150 men, women, and children of the Lakota Sioux had been killed and 51 wounded (4 men, 47 women and children, some of whom died later); some estimates placed the number of dead at 300. Twenty-five troopers also died, and 39 were wounded (6 of the wounded would also die).
It is believed that many were the victims of friendly fire, as the shooting took place at close range in chaotic conditions.
The site has been designated a National Historic Landmark.