FERGUS FALLS, Minn. - Prosecutors have charged a man and a woman from Minnesota with murder in the death of a 6-year-old boy they were caring for. Newly released court documents obtained by CBS affiliate KVLY indicate the boy, Justis Rae Burland, suffered horrific injuries.

Bobbie Bishop, 40, and Walter Wynhoff, 44, both face felony charges of second-degree murder, first-degree manslaughter, two counts of second-degree manslaughter and one count of malicious punishment of a child in connection to the April 9 incident. A sibling has been taken into protective custody.

Hospital staff and police said the boy was unresponsive when he was brought o a hospital. He was covered in scabs, scars, and marks from restraints; he also showed signs of internal injuries, the station reports. They were unable to revive him.

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Wynhoff told police that Bishop went up to the child's room Monday morning and started screaming, according to CBS Minnesota. When he ran upstairs, he noticed that the child was not breathing, and they drove to the emergency room.

According to the records, Justis' body was already cold when Bishop him to a hospital on Monday. He was wearing just a soiled diaper and a plastic bag on one foot. Hospital staff said they tried to revive him, but couldn't.

Justis's body was covered with cuts, scars, and burns from head to toe, and his open wounds were deeply infected.

Bishop told police that Justis and his brother had been with them since last August, when a friend's grandmother gave them up because of behavioral difficulties.

Wynhoff separately told officers that on Sunday, Justis was ordered to a 7-hour "time out" on his bed for wetting it. He also admitted that within the last four or five days of his life, the boy had been duct-taped to a wall.

During a later questioning, Bishop told police that their discipline of the children had escalated since a custody hearing in late March, and that she had beaten him with a belt around 20 times over the past month.

Bishop had a different account of the day they brought Justis to the hospital.

According to the court records, she told police that Wynhoff returned from Justis's room early Monday morning, and said he'd "never been so mad at a child" and that he'd slapped the boy. When she went to check on him, Justis was groggy, his speech was slurred, and he handed her a tooth that had fallen out. She saw a red mark on the side of his face.

According to KVLY reporters, Bishop went on to tell officers that she saw a broken stick on the bed next to him; officers later found two pieces of wood that tested positive for blood.