Friends say 18-year-old Kam Gill was killed in a crash between a tractor-trailer and a car in Brampton.
It happened around 2 a.m. Saturday on Airport Road at Lacoste Boulevard, south of Mayfield Road.
Paramedics said the victim, a male, had no vital signs when they arrived and a female was in critical condition.
A girl was sent to a trauma centre with serious injuries.
Two other people had non-life-threatening injuries.
Peel police Const. Thomas Ruttan said all four victims, who were riding in the car, were teenagers.
The area was closed to traffic but has since reopened.