At around 6:00 p.m. a driver went off the road on de Salaberry Boulevard, near the intersection of Davignon Road.
Her car ended up hitting the brick wall of a back yard.
Police aren't yet sure why the young boy sustained such serious injuries.
An eight-year-old girl and the driver suffered only minor ones, however, the woman did have to be treated for shock.
At this point, police aren't speculating on a cause, nor will they say if there were car seats in the vehicle.
They've ordered a full check of the vehicle to see if a technical problem could have played a role, and say no other vehicles were involved.