Missing Boy Was Killed Near School Before Anyone Knew He Was Gone (Exclusive)

NEED TO KNOW

New York teen Christopher Williams' family is claiming his school didn't ensure his safety and left them to face "an unimaginable loss"

The 15-year-old was struck and killed by a vehicle on the Southern State Parkway near Valley Stream, New York, on Thursday

"They failed my child. They failed my child," Christopher's mom tells PEOPLE. "My son goes to a special needs school. He's autistic. How can they let him run away?"

A 15-year-old boy vanished from his school last week and was soon hit by a car, his family says — with relatives claiming his school failed to ensure his safety and left them to face "an unimaginable loss."

Christopher Williams, of St. Albans, Queens, was struck and killed by a vehicle on the Southern State Parkway near Valley Stream, N.Y., about 1:15 p.m.