back in my sophomore year of high school (which would be about 20 years ago) the guy in the desk to the right of me had an epileptic seizure during class. at first i thought he was being goofy as usual, since he slowly turned his head towards me and had a dumb grin on his face with his eyes half closed, but then he started convulsing and fell over to his right, and HARD. the side of his head slammed into the desk in the next row on his way to the floor - split his earlobe, and i'm sure he had a hell of a knot on his head. his feet almost hit me on their way up as he fell over. thankfully one of his close friends who knew how to deal with it was also in the class with us, so she took over - had us get him on his stomach so he didn't choke, and had us all clear the desks out of the way while he flailed around on the ground, so he couldn't hurt himself any more than he already had, while someone else ran for the school nurse.
the simple fact that i remember that much detail over 20 years later shows how much of an impact it had on me. and having seen a seizure up close and personal, i can easily believe that your guy might have sustained those injuries even without anyone else hitting or shoving him. he could have easily fallen over while walking along, bounced his head off the curb and flailed/rolled himself into the street before essentially passing out. he's lucky you found him so quickly to stop/minimize the bleeding.