Mass grave at the Wounded Knee massacre. On 15 December 1890 Sitting Bull was shot dead. On December 28, 1890, units of the U.S. Seventh Cavalry captured a group of Minneconjou Sioux Indians at Wounded Knee Creek in southwestern South Dakota. The next day, as the Indians surrendered their weapons, a shot rang out, and then all the cavalry opened fire. At least 153 of the Sioux were killed (some estimate 300, out of about 350) -- most of them women, children, and unarmed men.