South Simcoe police responded to a 2-car collision on the 20th Side Road at Gilford Road in Innisfil around 8:30 Saturday night.
Witnesses reported a car was speeding and went through a stop sign.
Four people including a 4 year old boy were transported to hospital where the boy was pronounced dead.
The investigation is ongoing and the decision to lay charged will be made at a later time.
Names are not being released.