In Season 1, the killer is revealed to be Piper Shaw with Kieran being revealed in the second season as her partner. In the Halloween special, the killer is revealed as Tom Martin. However, some scenes are questionable.
- When a Stranger Calls (12th Episode)
The Killer's first confirmed action in the series. After being caught and taken to jail for his killing spree, Kieran is informed that someone is on the phone for him. He picks it up, and hears someone, using the Killer's voice, saying "Hello Kieran, who told you, you could wear my mask?", much to Kieran's clear surprise.
- Halloween (13th Episode)
The Killer's first confirmed appearance in the series. He sneaks into the prison using the vendilation vent above Kieran Wilcox's cell. The Killer slowly opens the vent to reach Kieran, but a security guard hears the vent creaking. When he turns around in surprise, the Killer jumps out of the vent, and brutally snaps/twists the Guard's neck 180 degrees, killing him.
The Killer then grabs the guard's keys and unlocks the cell door, freeing Kieran. Kieran walks out, facing the Killer. Kieran asks the killer who he is; the killer responds by slicing Kieran's throat open with his knife. As Kieran crawls away, trying to get the guard's gun, the Killer stabs him in the back of the neck, then twists the knife, killing him. After admiring Kieran's corpse, the Killer leaves before they could be caught.
The killer is revealed to be Kieran Wilcox, and he is also revealed to be Piper's accomplice. However, the finale confirms that there is more than one killer, and this new killer may have had some work in the first season.
Tom Martin is also revealed to be the killer in the Halloween, but had no action anytime else. There are some moments in the second season that could be attributed to the third killer, and one moment that was confirmed for a third killer.
- Kieran's kidnapping video: Emma is sent a video of Kieran tied up with his mouth duct taped. However, he is revealed to be the killer, so who was recording him? He may have recorded himself, but it seems unlikely.
- Recording of Emma at the funhouse: When Emma enters the funhouse to find Kieran, who is supposedly kidnapped, Audrey is sent a video showing that someone is recording Emma. Kieran is most likely getting ready to stalk Emma, but he might have still been doing it.
- Prison call: After Kieran is arrested for the murders, he gets a call in prison that seems like it is coming from the killer. But Kieran was getting the call, so it would have to be the third killer.
- Kieran and the prison guard's murders: 8 Months after his arrest, Kieran Wilcox and a prison guard are brutally murdered by another Brandon James killer. It was initially thought to be the Halloween killer, Tom Martin, but Tom confesses that he did NOT kill Kieran or the prison guard, so the third killer must have done it.
- Emma's attack at the mansion: This is presumed to be Tom Martin, due to the fact that he was wearing the same costume, but Tom wanted Emma alive before she rejected him, so why try and kill her beforehand?
- Brandon James: He is the prime suspect among fandom. He was revealed to have survived his gunshots at the lake near the end of Season 2. When Kieran was called, the third killer said "Who told you, you could wear my mask?" heavily implying the 1994 murderer is the person under the mask, due to being the first to use it. Brandon could also very well want revenge for Piper's death, and killed Kieran for his failure.
- Troy James: Another prime suspect of fandom. We have never seen and barely heard of Troy, Brandon's brother, before. Since he has never appeared in the series, he don't know where he was during all the murders. He could want revenge for Brandon and Piper. A man named "Mr. James" checked into Lakewood at the end of the Halloween special, and the desk clerk was calm when he entered, hinting the man might be a relative of Brandon.
- Kevin Duval: Another prime suspect of fandom. He is also the prime suspect of being the real 1994 murderer if it wasn't Brandon. His motive could have been that he was jealous of Brandon and wanted to frame him, have Maggie for himself. It is also heavily implied that he killed Kieran. In the Halloween special, he seen standing over Kieran's grave with a grim and unhappy expression on his face.
- Eddie Hayes: Kieran supposedly did not have any motive to kill Eddie, as he claimed he knew Audrey was working with Piper. He knew nothing about Kieran. Although it is possible that he killed him because he was going to reveal Audrey's involvement which Kieran was taunting her with, it is shown in When a Stranger Calls that someone is recording Ghostface stabbing Eddie.
- Quinn Maddox: Kieran was on the road to the barn. It took Emma and Audrey a few hours to get there. Kieran would have needed to get there before they did, although he knew that they were going there to begin with. After the murder, Kieran arrived at the scene in his car.
- Deputy Stevens: Kieran was still being pushed by Miguel to stand down as he pretended to plead Emma and Audrey's release. The killer was already ahead of them when they left. If the third killer didn't kill Maddox, he killed Stevens.