Originally Posted by sestivers

With all of the new information, I am now convinced that the front wheel fell off. What type of quick release (QR) do you have on the front wheel? It does not appear that the fork had the safety tabs (aka lawyer lips) installed on it, so you should be using enclosed (not exposed) cam QRs. If you weren't, this would have contributed to the wheel coming off. See this Sheldon Brown article to see what I'm talking about.

So my theory now goes as follows:
Front wheel QR is insufficiently tightened (even though it seemed to be tight enough) at home.
Bumpy road loosens the QR.
No safety tabs are in place to hold the wheel on with the loose QR.
Wheel comes out.
Fork is forcefully smashed into the pavement. On its way down, it goes through some spokes on the front wheel.
Fork breaks.

Originally Posted by DannoXYZ

Sorry to hear about your son's injuries. :(

I've been numerous crashes in races @ 30-40mph. One was at the Creston Road Race in SLO. Going down a straightaway, someone tangled up front and my teammate got hit on his handlebars from the side. Instantly turned his handlebars 90-degrees @ 40mph. Fork and wheel shattered instantly and he went over and had same injuries as your son, broken face and concussion. After we gathered up the pieces, we saw that one steel fork-blade had snapped off at the crown, the other was bent 90-degrees sideways. The rim had shattered into 5 pieces. Lots of bent and a couple broken spokes. But the hub was still firmly holding onto both fork-blades.

On your son's bike, if the fork-ends that broke off the fork weren't attached to the wheel, I'd have to conclude that the QR wasn't fully tightened. He may have hit a bump and gotten a little bit of air, or rode over a hole and the wheel dropped down. Once the front wheel came out, the fork hit the ground and broke. The spokes broke when they got caught up in the snapping fork.

Originally Posted by trin2du

Couldn't see it in the picture, but is the QR still attached to the wheel?

Originally Posted by San Rensho

Sorry to hear about your son's crash.

I think Stacey's question and the OP's answer pretty much sum it up. The wheel came out of the dropout. If the forks had snapped on their own (highly unlikely), the hub would have still been connected to the dropouts.

Sounds like this is what happened: The wheel comes out of the fork dropouts, one of the fork blades goes into the wheel and broke spokes, the fork ends hit the pavement and the forks snap.