So a zoo has a 400 lb creature in an enclosure which is easily accessible (obviously) for a 4yo boy to get in there and we are going to blame the parents?! Now I don't know these parents from Adam's house cat so I can't make any judgments about them. I didn't see what happened so I can't just assume (you know what you do when you assume) they were negligent. However, I do know a large and dangerous wild animal was kept in captivity for people's entertainment (place whatever value judgment on that you like - it's just a fact) and the animal's enclosure could be breached by a 4 yo boy, who is not the only person to have suffered a similar fate (it's happened with/to adults as well). I know in a situation like that you have to watch your kid like a hawk. Mine are grown and nearly grown and I still watch them like a hawk. I don't know what, if anything, the parents did wrong. I do know the zoo made it easy enough for the child to get in and the blame should, IMHO, should go primarily on those who designed and allowed to remain in place such an unsafe system.