A couple in Fergus Falls have been charged with the murder of a 6-year-old boy brought to hospital with horrific and historic injuries.

The criminal complaints against Bobbie Bishop, 40, and Walter Wynhoff, 44, state the boy and his brother had been subject to a period of physical abuse that included beatings with a belt, spankings and being tied up with duct tape.

The two boys had been in the couple's care, with their legal guardian living in Montana.

Bishop admitted to police that in the month leading to his death on Monday, the 6-year-old boy had been spanked 20 times with a belt, with Wynhoff saying Bishop administered the punishments, which had grown more frequent because of the boys' behavior.

The 6 year old was brought to the hospital in Fergus Falls by Bishop, who was panicking because he wasn't breathing.

He had injuries that medical staff called "disturbing," including blood infections from untreated wounds, "horrible sores" on his buttocks up to the back that were possibly from scalding water, and a strap mark on his left shoulder.

He had marks from head to toe, which police said were clear signs of abuse and neglect. Attempts to resuscitate the child failed and he was pronounced dead that morning.

Bishop and Wynhoff are facing five charges, including 2nd degree murder and 1st degree manslaughter.

The boy's brother has been taken into protective custody.