Christina Anderson, 44, was found with duct tape wrapped around her neck and mouth several times and her ankles tied with a plastic cable, the San Diego County Medical Examiner's Office said. Anderson had cuts in her neck that were likely inflicted through the tape after she died.
The coroner said she died from blunt head trauma. The cause of death was undetermined for Anderson's 8-year-old son, Ethan, whose charred remains were found in the rubble.
Investigators said they couldn't determine how Ethan died due to extensive burns and tissue loss. They said gunshot wounds, asphyxiation or burns from the house fire were all possibilities.
James DiMaggio, 40, was killed by FBI agents in the Idaho wilderness Aug. 10, one week after he allegedly abducted 16-year-old Hannah Anderson and killed Christina and Ethan Anderson at his home in Boulevard, 65 miles east of San Diego. Hannah Anderson was rescued and returned safely to California.
Christina Anderson asked DiMaggio to take Hannah to cheerleading camp Aug. 3 because she was at Ethan's football practice and unable to take her, San Diego County Sheriff's Detective Troy DuGal said in the autopsy report.
Hannah's disappearance triggered a massive search spanning much of the western United States and parts of Canada and Mexico. Authorities have said DiMaggio set fire to his home with a timer, giving him a 20-hour jump on them.
San Diego County Sheriff Bill Gore has called Hannah "a victim in every sense of the word." He has declined to discuss a possible motive and investigators haven't publicly addressed other aspects of the case, including why the family went to DiMaggio's home, and how Hannah was treated in captivity.
The autopsy report says Christina Anderson suffered blows to the back of her head, forehead and nose but doesn't describe which instruments were used. Authorities have said firefighters found a crowbar near her body.