The boy, Jacoub Favila of Ajax, Ont., was one of six children and two adults riding in a van travelling west on Highway 401 near Dixie at about 4:30 p.m. Tuesday when it was hit from behind by a silver Hummer, said OPP.
"I'm just broken right now," Bloomy Favila, Jacoub's mother, told CBC News in an interview at the family home in Ajax.
The boy was rushed to hospital, but he succumbed to his injuries late Tuesday. The other occupants of the van were not seriously injured.
The Hummer was driven to the Dixie Road area, said OPP, where it was abandoned by the driver. Police are still searching for the driver.
"We have no description at this time. Whether it's male, female, and whether the person sped on foot," said OPP Sgt. Dave Woodford.
Bloomy Favila choked back tears as she talked about her son.
"Just help us find the one who did this to our son," she said.
Family friend Gina Pan says his twin is having a hard time understanding why Jacoub hasn't come home.
He thinks "it's just another game or something like that," Pan said.
Bloomy Favila says there is only one thing her family wants to see happen now.
"Justice for Jacoub ... justice for Jacoub, that's it."
CBC News has learned that the abandoned Hummer is connected to a Toronto car rental company.
But the company is not saying publicly whether the vehicle was stolen, or rented at the time of the deadly crash.