Well, one can only hope that all of the victims lost consciousness who didn't die immediately. The only good part about our brains when it comes to things like that is when we endure a lot of pain our brain knows to shut off consciousness to spare us some of it. But we won't really ever know how any of these kids suffered beyond what the autopsy reports say.
Heck I was in a car accident back in 2009, I flipped my car and I was out for about a full minute or two cold. I must have hit my head because I don't remember the car flipping and I was not really in any pain when I woke up. (the next day I was in a LOT of pain, lol)