What exactly happens to Bryan? *Spoiler*

[BrainSushi]

Okay, so Barry's son Bryan falls off the horse, and gets a good whack on the head, but what exactly kills him? What is it that he died of?

[Gold Trumpet]

exactly that. horse injuries can be very severe, especially to a kid trying to ride an adult sized one.

~rougerum

[Royal Tenenbaum]

He probably had a ton of internal hemeraging, and died from it.