A soccer coach who a California family says was the last person who had contact with their dead son is a person of interest in the boy's disappearance and was arrested on an unrelated sexual assault case ... TMZ has confirmed.
Missing 13-year-old boy Oscar Omar Hernandez was found dead in a ditch earlier this week in Oxnard and his family says he was last seen with his soccer coach, 43-year-old Mario Edgardo Garcia Aquino.
Our law enforcement sources tell us .