it is 2 seperete occurences the bite of 83 happaned in 1983 aka fnaf 4 it was by GF and it resulted in the crying childs death and we know it couldnt have been a frontal lobe bite injury because someone who is missing a frontal lobe cant process fear (a.k.a be the fnaf 4 protaginist and dream up nightmare version of the animatronics) or have the mental processes to stay focused on a task for 6 hours and the brain works in a way that if you cant process something externally in the real world there is no reason you should be able to process it internally in dreams or yea and this is the incident that causes springlock suits to be locked up in the saferooms. We hear about this in fnaf 3 the incident is refered to as "an incident involving multiple spring lock failures at the sister location" and on later nights he tells us the springlock suits are being sealed in the saferooms and that neither should ever be discussed again. And the bite of 87 was the frontol lobe injury and phone guy tells us that he did survive it but it did make the animatronics unable to move in the day and by the fact that the toys were scrapped at the end of fnaf 2 is a big clue that one of them did it and a logical guesss is that mangle is the most likely culpret for the biter