How old was the kid?
We went to the zoo plenty of times and we always knew we weren't allowed to climb up on the enclosures or try to touch the animals, except in the "petting zoo" part. So yeah, it probably wasn't the kid's fault, but obviously the parents had done a bad job of parenting beforehand. It wasn't just a case of "turn around and the kid's in the bear pit".
He was four. Apparently he climbed a wooden fence and then went over and put his hand thru the chain link fence. Park officials speculated he'd been eating so the food scent was on his hand.