FAYETTEVILLE, N.C. -- An autopsy has found a 19-year-old woman found dead in a North Carolina river was found naked with a zip tie around her wrist and was violently killed by someone else.

Media outlets report that the pathologist couldn't give an exact cause of death for Kristen Stone, whose body was found in the Cape Fear River by a fisherman on Aug. 9. But the autopsy suggests she could have been smothered, suffocated or drowned.

Authorities charged 33-year-old Charles Cottingham with first-degree murder in Stone's death. Court records indicate Cottingham was charged with sexually assaulting Stone a year earlier in Hoke County.

Authorities say in that attack he held a gun to her head and made her perform a sex act.