The Wounded Knee Massacre was the last major armed conflict between the Lakota and the United States. It was described as a massacre by General Nelson A. Miles in a letter to the Commissioner of Indian Affairs. On December 29, 1890, five hundred troops of the 7th Cavalry Regiment, supported by four Hotchkiss guns (a lightweight artillery piece capable of rapid fire), surrounded an encampment of the Lakota bands of the Miniconjou and Hunkpapa with orders to escort them to the railroad for transport to Omaha, Nebraska. By the time it was over, 25 troopers and more than 150 Lakota Sioux lay dead, including men, women, and children. It remains unknown which side was responsible for the first shot; some of the soldiers are believed to have been the victims of "friendly fire" because the shooting took place at point-blank range in chaotic conditions. Around 150 Lakota are believed to have fled the chaos, many of whom may have died from hypothermia.