PIERRE - United States Attorney Ron Parsons announced today that U.S. District Judge Eric C. Schulte has sentenced a man from Dupree, South Dakota, convicted of Voluntary Manslaughter. The sentencing took place on July 13, 2026.

Gradyn Blue Arm, age 27, was sentenced to 12 years in federal prison, followed by three years of supervised release, and ordered to pay a $100 special assessment to the Federal Crime Victims Fund.

Blue Arm was indicted in September 2025. He pleaded guilty on April 9, 2026.

The conviction stemmed from an incident that occurred on June 3, 2025, within the Cheyenne River Sioux Indian Reservation. After being asked to leave a residence in Dupree, South Dakota, Blue Arm returned to the location armed with knives. Blue Arm argued with the victim and others in the front yard before walking away from the residence. The victim and two other individuals followed Blue Arm. Soon thereafter, Blue Arm stabbed the victim in the abdomen with a knife, which resulted in the victim's death.

This matter was prosecuted by the U.S. Attorney's Office because the Major Crimes Act, a federal statute, mandates that certain violent crimes alleged to have occurred in Indian country be prosecuted in federal court as opposed to state court.

This case was investigated by the FBI and Cheyenne River Sioux Tribe Law Enforcement Services. Assistant U.S. Attorney Wayne Venhuizen prosecuted the case.

Blue Arm was immediately remanded to the custody of the U.S. Marshals Service.