I would go with everyone else here... exhaustion... plenty of stories i've heard of the big boys running themselves into the dirt with the 2 f's this time of year...
The brain damage theory sounds very interesting as well... if his ears where tore up and damaged rack already then if he did have a hemorage or swelling he could of acted and died just like you said... take a look at his noggin... check it out and let us know.[&:]