Abuse

A 5-year-old Arizona boy died after being left inside a scorching hot car for hours while his family hosted a huge gathering ... and now his parents are facing serious charges.

Theo Sabo was found unresponsive Sunday afternoon inside a vehicle outside his family's Peoria home ... where temperatures climbed to around 106 degrees.

Police say the family had returned home from another child's baptism around 1 PM and was hosting a party with dozens of friends and relatives ... but Theo apparently never made it inside.