Ok I've seen the mistakes happen teaser. I don't know if anyone thought of this but what if Vinnie's teaser from FNAC 1 was foreshadowing the Fnac 3 Puppeter's mistake.
He was fighting with the Rat who was choking him. He shoved him away and killed him. He didn't want to tell because he feared losing everything. The cat said it was a mistake and he thought. "I shouldn't pay for a mistake" He compressed his guilt by saying. "Mistakes happen" He tries to convince himself he shouldn't pay his life of a mistake. And even he believed it was a mistake. It shows the rat which is HIS mistake. He made the rat and he did it by accident. That was his mistake killing him and creating the rat.