William Afton (Five Nights at Freddy's)

"you can't"

- The Killer

"Follow me."

- The Killer, luring the animatronics to the safe room.

The Killer (or the Purple Guy/Man or The Murderer) is the main antagonist of the Five Nights at Freddy's series. He is also the hidden main antagonist of Five Nights at Freddy's 3.

The Killer was a man who dressed up as one of the mascots at Freddy Fazbear's Pizza (theorized to be Golden Bonnie or Springtrap) and used his kid-friendly disguise to lure five children into the back of the pizzeria. He then murdered them and stuffed their remains into the mascots' costumes (Freddy, Chica, Bonnie, Foxy, and the Puppet). He was arrested the following day and charged, but his current status and influence on the game's events is unknown (although the third game confirms the one who was caught was just a scapegoat). The prequel states that the killer was a purple man who is possibly one of the security guards.

Role in the franchise
A man who no one has ever seen or heard of emerged in Freddy Fazbear's Pizza with plans of death and chaos for the company simply for the sake of it. A man with no name or motives, a villain driven by a lust to create social disorder and desired nothing but anarchy to feed his sadistic appetites and morbid, dark sense of humor.

One day, in Fredbear's Family Diner, as Fredbear was serving cake to the children, a child was crying outside for an unknown reason. As he cried, a man drove over in a purple car and murdered the child. Fredbear could not protect the child, for if he was to venture outside the pizzeria he would be deactivated (as stated by Phone Guy in the third game). With that, the man drove away leaving the child's corpse outside. The child, driven by revenge, possessed an animatronic a certain time after that, known as the Puppet.

Years later, the man returned to the pizzeria and found a yellow suit of an old animatronic and lured six children to a quiet part of the building and murdered them. He placed them all in the old animatronic suits, placing the sixth child inside a golden Freddy suit. He managed to frame possibly two people (the Dayshift Guard and Jeremy Fitzgerald) for his heinous crimes and once again got away with no punishment. The Puppet, even more enraged by his crime, gave the children their lives back, in the form of the animatronics.

Years past and Freddy Fazbear's Pizzeria opens once more, only for the man to return. This time the man killed five children outside Pirate Cove, pinning the blame on the animatronic within, causing it to be deactivated and Pirate Cove shut down. After this, Fazbear's was to be closed again, seemingly forever. And the man would not return to the pizzeria for years.

Five Nights at Freddy's 3
The Killer appears in Five Nights at Freddy's 3 as the true main antagonist of the game, inhabiting Springtrap in the present day. He appears in the mini-games that act as cutscenes between each night. Instead of murdering children like in the previous game, however, he lures the animatronics one-by-one with a "Purple Freddy" suit (possibly Shadow Freddy), and then ambushes them and dismantles them. In the "Bad Ending", you play as the crying child who seems to be the ghost of the Puppet or one of the original five animatronics. After floating around the pizzeria, the player will eventually find a room filled with the other dead children and the Murderer himself, who seems to be panicking. When the player approach the Murderer, he will run away from them. Eventually, the Killer is cornered by the ghosts of the five murdered children. Attempting to flee, the Killer hides inside of Springtrap in order to protect himself. He stands up and laughs at his victims, thinking he has won, but due to the rain dripping from the ceiling the suit closes in on him like an iron maiden (presumably caused by the suit's spring trap, hence the name of the character), gutting the Killer to death and ending his physical reign of terror, but also possibly allowing him to possess the animatronic as a zombie, due to the teaser images of Springtrap showing the Purple Guy's corpse inside.

In the ending of the game, "Fazbear's Fright" burns down, presumably destroying both the animatronics and the remains of the Killer's body, killing him once and for all (although the brightened image of the newspaper image at the end shows that Springtrap could possibly still be alive).

In the mini-game "Happiest Day", it shows the spirits of the the children leaving the animatronics, meaning the Killer's death finally set them free into the afterlife.

Five Nights at Freddy's 4
The Killer can be seen in the mini-game of Night 4, presumably helping one of the employees put on the Spring-Bonnie suit and is heavily implied to be the father of the child protagonist of the game.

Personality
The Killer is the confirmed murderer of the children that sparked the downfall of Freddy Fazbear's Pizza and started the chain of events that leads players through the series.

Judging by his actions and appearance within the mini-games, the Killer is cruel and uncaring, taking sadistic pleasure in his crimes with a smile. It isn't until he is confronted by the ghosts of the five kids that he shows any other emotion - panic and concern for his own life. His motives are unknown, but deliberate.

Theories
Prior to the revelations of his fate at hands of the animatronics in the third game, there are several theories based upon clues that can be found in the prequels, which are:
 * In recent theories, several fans of this game have theorized that the Killer is really the security guard that the player plays as Mike Schmidt and later Jeremy Fitzgerald. Several hints throughout the game also indicate that this is all in the Killer's mind:
 * In the game, if the player manages to beat all five days, they will receive a check of $120.00, and since the player has to endure six hours (12:00am to 6:00am) for five days, the player receives $4 an hour. This hints that this game takes place somewhere between late 1980s and to 1995, but sometime after the The Bite of '87. Also the check player gets upon beating Night 5 is dated for November 1987.
 * It was hinted that the Killer may have been the one responsible for the Bite of '87 for tampering with the animatronic, which resulted in one of them biting the frontal lobe off a child. If the player endures the 7th night, the player receives a pink slip (or a termination slip), for tampering with the animatronics, general unprofessionalism and odor. So, for revenge, the Killer disguised himself as a mascot, lured five children and stuffed them in the animatronics, hoping that the place will be forced to close down.
 * Even though the reports never say that a former employee was the Killer, the killer must've had access and knowledge of the Employees Only Room very much like Mike Schmidt himself.
 * While in the security room, the player can spot cobweb and right window of security room is seemingly broken if turn on the light for Chica to be there, indicating that Freddy Fazbear's Pizza is already closed down.
 * There could be two killers, due to the fact that there are two different sprites of him (pink and purple).
 * There's a possibility that the Phone Guy is the perpetrator due to the fact that The Killer had a phone on his hand and a security guard badge on him. Though after the third game, this may not be true.
 * There are other hints that the Phone Guy was The Killer as well as the phone-like object he uses in the second game. This includes how the Phone Guy said he liked Foxy the best and disliked the Puppet, shown by how The Killer smiling at the former in the "Foxy Go Go Go" mini-game while the first dead child resembled the Puppet in the "Take Cake to the Children" mini-game. Another part is how both The Killer and Phone Guy knew about the Spring-Lock suits. The fact that he knew how the suits worked and where they were kept: in the Safe Room at the back, a place where the Animatronics cannot go.
 * There is a counter to this, being if the Killer knew how they worked, he would've prepared the suit properly. However on Night 3 of the third game, the Phone Guy's recording stated "Do not breathe on the spring locks, as moisture may loosen them, and cause them to break loose." Carefully paying attention to the minigame showing The Killer's death and rebirth as Springtrap, there could be stormy weather heard and rain was leaking in. This can more then likely be the reason why the locks went off and killed The Killer.
 * The final piece of evidence was during the first game during Night 4. Phone Guy's message told the player "Uh, hey, do me a favor. *bang bang* Maybe sometime, uh, you could check inside those suits in the back room? *bang bang* I'm gonna to try to hold out until someone checks. Maybe it won’t be so bad. *bang bang* Uh, I-I-I-I always wondered what was in all those empty heads back there. *chime plays*." This foreshadows Phone Dude finding Springtrap.
 * A theory is that Golden Freddy, is implied to be the very animatronic that the Killer once modified into actual costume before committing his killing spree.
 * Fans said that the second killer is Fritz Smith the guy's name was shown on the pink slip in FnaF2 when you complete Night 7. Fritz may be the second killer because when you beat night 7, the pink slip says that he was tampering with the animatronics and it was his first day on the job.
 * Some people have made theories the little kid being haunted in the fourth game is the Purple Guy as a child and that he is actually scared of the animatronics. This theory seems to make sense, as it could be explaining why he murdered the children at the same location, as he wants to shut down Fazbear's Pizzeria.
 * There however is the fact that the killer would have then lost his frontal lobe making it more difficult then you think to do what he did which he seemed to do easily. Not to mention the child's crippling fear of the animatronics no doubt he wouldn't go inside one to start the chain of murders.
 * This is reinforced by how at the end of the game you hear a flatline implying the child died making it impossible for him to be the killer.

Trivia

 * The Killer seems to like Foxy as he smiles at him as he exits Pirate's Cove in one of the Death Minigames. If this is why The Killer was smiling, it further suggests the theory that he is Phone Guy, as of this line, "Did Foxy ever appear in the hallway? Probably not. Like I said, he was always my favorite."
 * He also seems to dislike the Puppet.
 * If the minigames are based on true events within the game (the crying child and the children in the Pirate Cove minigame), The Killer has murdered 10 to 11 children.
 * The Killer's motivation for killing the children is still a mystery, although many people assume he did simply for his own enjoyment. The reason he kept returning to the same location is unknown, however.
 * Before his actual fate revealed, people assume that the Phone Guy is the Killer due to him holding what appears to be a phone and wearing a badge in the minigames much like Phone Guy does. The reason the Killer is holding a phone is still a mystery, although it may not even be a phone at all.
 * He is somewhat similar to Freddy Krueger.
 * Both are child killers who enjoy what they're doing (the Murderer is always seen with a smile on his face).
 * In death, they became even more powerful than they were in life.
 * The Killer is noticeably the only Five Night's at Freddy's villain to be truly evil and malevolent. While most other major villains are ambiguous and may not even be that evil, the Killer commits all his atrocities expressly out of his own free will.
 * The Killer ironically dies the same way he killed the children: being stuffed inside an animatronic suit.
 * His death was an accident due to one of the instructions from the Phone Guy was not to touch the springlock or breathe on it as moisture would cause the springlock to snap. The killer was laughing/breathing while in the suit, presumably causing moisture that resulted in the springlocks to snap and crush him in the suit.