Me and Alpha were discussin it earlier. (SPOILERS) Everything hints at the bite of '87. Found on the wiki: "On the A.I. settings for the Custom Night in the first game, entering 1/9/8/7 will cause Golden Freddy's kill screen to appear and crash the game." which might have hinted all along it was golden freddy's animatronic biting the victim.
Then again the phone guy says FNAF1: "I-It's amazing that the human body can live without the frontal lobe, you know?" The kid actually might have survived.
When you think about it, in the game you meet children, but they're not there when the kid dies. Also the brother leaves the kid alone there. Also all the toys and mangled at his house. Did the kid and his brother have an exclusive entry to the pizzeria? they must have known the owner...
Then, there's a small scenario with purple guy putting a suit on a human. He's working there day time (or end of night time preparing daytime workers when no one's allowed in the place). Maybe hinting he was the only one to know how to put them safely on others. (hence why he could wear them too maybe hinting to other games).
This would be the very first restaurant with only "golden freddy" and "golden bonnie". Golden Freddy might never have been freddy, but "fredbear", the very first mascot, then springtrap was created, but that they had multiple of these two costumes made for wearing but only two animatronics made for the show (those two we see singing on the bite of 87). Most likely since the animatronic ones were decommissioned, they could only send worn out human suits (why they would be out of order for certain time) to put back a skeleton into them in other restaurants. I'm not sure but it's possible that there might have been a sister location to Fredbear family dinner, which would have been Freddy fazbear's pizza (the first), and that would have been there that freddy bonnie chica and foxy would have been, then "golden freddy" (fredbear) sent to (that would be why he's in the first game). so technically, a older restaurant with only springtrap and fredbear, and a newer one with better animatronics (Freddy,Bonnie,Foxy,Chica) happen at the same time. And then FNAF 2 happen, the "old models" are being hidden and new ones are used because of the bite.
I honestly don't believe it is. The kid was bitten by Golden Freddy/Freddy Fredbear, wasn't he and Springtrap in the first restaurant? Why would they be in use in 87? I don't know if I'm right or wrong, this is what I'm thinking. I get the feeling there was another bite victim that we were never told about. That kid had his whole head crushed in. And holy hell! That was freakin' evil of the brother! How heartless can you be to do that to your kid brother?! Where the hell was their parents?! Good God.
I'm with the majority assuming this: Purple guy saw these kids bring the little boy to the animatronics and what happened to him. And as "revenge" or "justice" killed them and stuffed them into the suits.
Another section believe that the victim died and later possessed golden freddy and thats why hes all ghosty. (Idk if I believe this but ya'know)
Call the police, their parents, call child services...right after I fainted or threw up from seeing the blood and whatever else that came out. Weak stomach, but that's just me. Someone crazy would probably go and kill those kids.