Gutterballs

BBK stands for the bowling centre's caretaker Egerton, whose name appears on the scoreboard as a mysterious player. The scoreboard initially shows BBK as a glitch, but after each murder, skull-and-crossbones strikes appear beside his name, serving as a grim tally of the killings.

The BBK entry appears on the scoreboard before any murders occur, hinting that the killer has been present since the beginning.

Lisa kills Steve. After being sexually assaulted by Steve and his group on the first night, Lisa returns traumatized on the second night. She confronts Steve and kills him with a weapon, taking her own revenge before Egerton's final reveal.

Lisa's trauma and return with Jamie on the second night signal her intent for vengeance.

Egerton witnesses the sexual assault of Sam on the first night while he's downstairs but cannot intervene in time. The horrific crime and his failure to stop it appear to trigger his transformation into a vigilante killer, targeting those responsible for the violence.

Egerton's presence during the first night's assault and his inability to stop it plant the seeds for his later actions.

Egerton spares Patrick despite his involvement in the group assault because Patrick is the only one who shows remorse and voluntarily confesses to his role in the crime. Egerton tells Patrick he was spared for reasons he refuses to disclose, leaving his motive ambiguous.

Sarah kills Jamie because she suspects he did nothing to prevent the murders or stop the violence throughout the night. With all the BBK members dead, she turns on Jamie, viewing him as complicit through his inaction, and executes him before the survivors can escape.

Jamie is shown as part of Lisa and Egerton's plan, making his trustworthiness questionable to Sarah.

Lisa intervenes in the confrontation between Steve's group and Jamie's crew by dropping a bowling ball on Steve's foot. This shocking act breaks up the initial brawl and establishes Lisa as a willing participant in the group's violent dynamics, foreshadowing her later role as both victim and perpetrator.

Lisa's aggressive intervention establishes her as a character capable of using violence to resolve conflicts.

Sam goes to the bathroom to freshen up and is lured into a stall by a noise. The killer forces her to swallow a bowling pin, kills her, and then castrates her body with a switchblade. The killer also chains the bathroom exit to trap the remaining survivors inside.

Jamie kills Egerton in the final confrontation. After Lisa slits Egerton's throat but fails to kill him, Jamie wrestles with him and finally shoots his head off, ending the caretaker's killing spree.

Lisa confronts Egerton to understand his motivations, particularly why he killed so many people and why he spared Patrick despite his involvement in the assault. Her confrontation leads to her using Sam's switchblade to slit Egerton's throat in revenge for the night's violence.

The skull-and-crossbones strikes appear beside the BBK entry after each murder, serving as a grim scoreboard tally of the killing spree. After Dave and Julia are killed in the bathroom, two skull marks appear, confirming that the BBK marker is not a glitch but a real-time record of the murders.

Steve discovers Joey's headless body in the pinsetters area while investigating the sounds of the machinery. The killer ambushes Steve there, and he attempts to fight back but is bludgeoned with a bowling pin and killed.

The masked killer kills Dave and Julia in the bathroom while they're kissing in a stall. The killer suffocates them both in a compromising position, and their bodies are discovered after the murder. This is the first confirmed murder that connects the BBK scoreboard to actual deaths.