Cayo will be sentenced Nov. 4. Third-degree rape is punishable by up to five years in prison. Second-degree assault is punishable by up to one year in prison. He remains in Pierce County jail.
According to charging documents, two other boys, 15 and 13, each face one count of second-degree rape and second-degree assault, and a 17-year-old boy faces a charge of unlawful imprisonment.
The victim was found half-conscious and severely injured. She had been sexually assaulted and repeatedly burned with a lighter. The teens had been drinking vodka together when the girl passed out and was attacked.
The assailants recorded the attack and posted it on the internet with Snapchat, an application that deletes images seconds after they are opened. Detectives were able to recover the files.