An autopsy shows the man whose body was found behind an elementary school in the Town of Beloit apparently died of an overdose.  Several law enforcement agencies working together tracked down 26-year-old Corey Sandoval and arrested him Sunday morning.  A release from the Town of Beloit Police Department says Sandoval was taken into custody on a duty to aid victim charge.  He’s being held in the Rock County Jail.  The body was found Saturday at Townview Elementary.  Results of toxicology testing will be needed to confirm the overdose as the official cause of death.