Going Snake Massacre

Resulting from a jurisdictional dispute between the U.S. government and the Cherokee court system, the Going Snake Massacre was a shootout in the Going Snake District of the Cherokee Nation (present-day Adair County, Oklahoma) on April 15, 1872, between U.S. marshals and Cherokee citizens. Ezekial "Zeke" Proctor, a Cherokee, was being tried in a Cherokee court for the killing of Polly Beck, also a Cherokee, and the wounding of Jim Kesterson (or Chesterson), a white man. Believing that Proctor would not receive the punishment he deserved in a Cherokee court, Kesterson had petitioned a federal court to have him tried by the federal court, and ten marshals were sent to arrest Proctor in case he were acquitted by the Cherokee court.
Before the trial even got started, however, a shootout erupted between the marshals and Cherokee bystanders, who resented the presence of the federal law officers. Seven marshals and one Cherokee were killed, and several people wounded. The next day, Proctor was acquitted in the Cherokee court, which was allowed to retain jurisdiction. There's a lot more to this story, but I'll save it for another time.