Christmas Cruelty

A man brutalizes a family whose home he has broken into, raping the mother in front of her bound and gagged loved ones before murdering all of them, starting with the baby, who he eviscerates with a circular saw. Elsewhere, three friends named Eline, Magne and Per-Ingvar celebrate the holiday season by making decorations, pulling pranks and getting drunk. The next day, while the trio recover from their hangovers, the killer, revealed to be a loving family man and a NAV employee, begins stalking them after stumbling onto Eline and Per-Ingvar's case files, at one point telling his wife, "I can't stop thinking about a poor girl and a guy in a wheelchair. They are going to have a horrible Christmas. I have to contribute in my own way, so they don't have to worry about the new year at least."
Per-Ingvar holds a small Christmas party at his apartment and unintentionally injures one of his guests, who Magne escorts to the hospital, accidentally leaving the door open on his way out. The killer, disguised as Santa Claus, barges in, fatally bludgeons one of the revelers, and sexually assaults Eline while Per-Ingvar is forced to watch. Before the killer can finish he is interrupted by a pair of late arrivals, one of whom he decapitates before incapacitating the other. Returning to Elise, the killer stabs her in the genitals and performs cunnilingus on her before he resumes raping her, knifing and smothering her when she begs him to stop. The killer cleans himself up afterward, makes dinner (which he eats while seated on Per-Ingvar) and spends the night at the apartment. In the morning, the killer uses Per-Ingvar's debit card to purchase a chainsaw, which he uses to dismember both Per-Ingvar and the remaining party guest. Answering a call from his daughter, the killer reassures her that he will be home soon as he writes "Merry Christmas" in blood on one of Per-Ingvar's walls.