The man could be dead. Wow! You don't really want to brand an adult horse, trust me. Horses are tough enough to control at the best of times. We restrained our animals a bit more than that when we branded.
I recall that film clip, or a virtually identical one, from years ago on television. IIRC, that guy wasn't badly hurt. But then, who remembers correctly? I didn't know that horses were particularly dangerous as biters. Ya gotta feel for that poor kid.