Blame it on Wovoka the Piute. He is the one who got the Ghost Dance craze started.
Also, Bourke, in the book ON THE BORDER WITH CROOK states that when the tribes, in 1876, traded for tube fed lever action rifles, the got “surly”. This was just before the Sioux war of that year, the Rosebud and Little Big Horn fights in which they cleaned Custer’s clock.
The Ghost Dance had everyone worried that this meant a return to what happened in 1876 so they tried to disarm the tribes.
https://www.pressreader.com/uk/daily-mail/20160119/282780650510937
“A. R. Morris, Brighton. A miscommunication at Wounded Knee led to one of the worst massacres in American history.
Major Samuel M. Whitside and his troops intercepted a band of Lakota Sioux trying to reach the Pine Ridge Reservation. escorting them to Wounded Knee Creek, they demanded that the tribe hand over their weapons.
A young native named Black Coyote, of the Minneconjou tribe, raised his Winchester above his head, shouting that he paid much money for the rifle and that it belonged to him.
When a trooper tried to take his rifle from him a scuffle ensued, during which a shot was fired into the air. Panicked, the soldiers took the shot as a sign to open fire on the tribe. Some Lakota managed to seize weapons and return fire, but they were cut to pieces by field artillery on the surrounding hills.
As the Lakota fled, cavalrymen gave chase — some bodies were found miles away from the initial battle site. more than 250 Lakota and 25 U.s. soldiers are believed to have died.”
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It should be also noted that some say a Medicine Man reached down, and threw dust into the air as a signal for the Indians to start shooting, the first shot mentioned here.
Good summation.