William Afton kills children in Five Nights at Freddy’s because he is written as a serial child murderer driven by jealousy, cruelty, and, in many interpretations, a desire to experiment with the supernatural “remnant” and gain power or immortality. The series never gives one single, fully confirmed motive, so most explanations come from hints in games, books, and fan theories rather than a definitive in‑story confession.
In-universe motives
Many fans read his first murders as coming from jealousy and resentment toward his business partner Henry and Henry’s family, especially Henry’s daughter Charlie. Killing Henry’s child and later other kids is often interpreted as a way for Afton to hurt Henry and destroy his success and happiness.
Later, the series introduces remnant, a substance linked to souls and possession, leading to the theory that Afton continues killing to study how children’s spirits can be bound to animatronics and used to pursue immortality or control over life and death. In some book material, he is also described as feeling empty and enjoying the act of killing, suggesting that at least part of his motive is simple sadism.
Differences between versions
In the games, his motives are mostly implied through background details, minigames, and secret scenes, so players piece together that he is a remorseless serial killer who targets children connected to the restaurants and animatronics. In the novels and some fan discussions, extra emphasis is placed on his jealousy of Henry, his broken family, and his obsession with creating a “perfect” or permanent family by trapping souls, which expands on but does not strictly canonize his reasons in every continuity.
What is actually confirmed
Across versions, what is consistent is that Afton willingly lures, kidnaps, and murders children and hides their bodies in or around animatronics. What is not fully confirmed is whether jealousy, grief, experiments with remnant, or pure enjoyment is the primary cause, so any detailed explanation is best treated as theory supported by scattered lore rather than a single official answer.
