Police said they found videos of Hurley being beaten, the AP reported.
Prosecutors said an autopsy found bruises on the boy's body, but that he died from trauma to the head, the AP reported.
Officials said Roush admitted that he's the person seen on the video hitting the boy, the AP reported.
Batts told law enforcement officials that Hurley had been living with her, Sasser and their children for about two years after his father died, KPAX reported.
Hurley’s mother told detectives that she had tried to call her son, but Batts wouldn’t allow her to talk to her.
Batts said Hurley's behavior became an issue after his father died, adding that the 12-year-old was drinking alcohol and stealing. She and the other relatives Hurley lived with said that he was self-harming, hearing voices and that he was suicidal, KPAX reported.
The 14-year-old uncle said that Hurley ran into an entertainment center's corner which left a large cut and a head injury, according to KPAX.
The teen told detectives that he saw Hurley standing over Batts with a knife, so he tackled and punched him several times.
Hurley weighed 103 pounds and was 5 feet, 3 inches tall. The 14-year-old is about 300 pounds and 6 feet tall.
Batts said Hurley and his uncle fought on Feb. 2 and that Hurley slept on the floor that night, mumbling and moaning. Batts said she found her grandson dead on the morning of Feb. 3, KPAX reported.
Sasser, Batts and the uncle face felony deliberate homicide charges. Roush was charged with felony assault on a minor, The Bozeman Daily Chronicle reported.