Theory by Treesicle:

You thought Fnaf1 was the first? Well, you're about to be proven wrong. Fnaf 1 is actually a prequel. Or one of out of the 3 prequels there are. What actually came first timeline wise? Fredbears family diner came first. This might not be surprising. Then the bite of 83 happened blah blah blah. Then Fnaf 4 happened. It is believed that fnaf 4 is a dream. But, I don't think so. Fnaf 4 takes place in the house of the bitten Child. So it was Fredbear, and then Fnaf 4 in the timelines. After those two, came sister location. I will be doing a next chapter of the Afton family and which order of events they died in. Anyways, Sister Location is the 3rd timeline because there is a place where you type in a specific number. If you type it, it shows you the Fnaf 4 house. Which means Sister Location is actually UNDER Fnaf 4. Shocking ain't it. After those 3 places, its either Fnaf 1, Fnaf 2 next. Fnaf 3 is the last one because the pizzeria burned down. Of course.

Why Isnt William afton the murderer? He didn't create the animatronics. Henry did. So that means he created the 3 killer animatronics that exist in the timelines. Fredbear, Circus Baby, and the 3rd Animatronic who did the bite of 87. He apparently installed a killer claw in Circus's stomach, made to kill all alone children.

In the Fnaf minigame, where William tells you to follow him, he rips you apart, right? But he is only trying to set the children free. He thinks by disassembling the animatronics they will be set free. The ghosts misinterpret this and think he's the murderer. So they chase him to the springlock suit, forcing him to get inside the suit. He laughs at them because wouldn't you laugh when someone couldn't get you? Like in tag? Well he died a horrible death. After his death, and after fnaf 2 came, he set the pizzeria on fire. It was his last attempt to free himself and the souls. It may or not worked. The book sliver eyes was only made to throw you off the scent. It is totally different from the games.