Si Tanka (Spotted Elk), whom U.S. soldiers called Big Foot, is known to have participated in the Sioux victory at the Little Bighorn, though his exact actions are unclear. However, since he was about 61 years old, his role, like that of Sitting Bull, was probably one of generalship rather than front-line warrior. After the Little Bighorn, he and his followers were involved in several skirmishes with the U.S. Army before settling onto the Cherry Creek Reservation in present-day South Dakota. Here they led a generally peaceful life until 1890.

Si Tanka and his followers were believers in the Ghost Dance ritual, which they thought would resurrect their dead loved ones and bring back the buffalo. The Indian Agents, who were convinced that the Ghost Dance made natives hostile to Europeans, sought to suppress its practice with the help of the army.

After Sitting Bull was killed, many of his followers joined Si Tanka's band. Fearing the U.S. Army's reaction, Si Tanka, by now 75 and near death with pneumonia, fled with his followers. The reorganized 7th Cavalry overtook them on December 28, 1890, at Wounded Knee Creek (present-day South Dakota). The following morning the cavalry opened fire on the camp.

When the smoke cleared, Si Tanka and between 200 and 300 Sioux, mostly women, children, and elders, lay dead. In the confusion, 25 American troopers were also dead, probably at the hands of their own men.