<P> Katrine believes that Arve Stop (J.K. Simmons), a business tycoon implicated in the earlier case, is behind her father's death . Stop is involved in a high - class prostitution ring overseen by Idar Vetelsen (David Dencik), a doctor working at the hospital all the current victims had gone to . Britte's cell phone begins transmitting again, and the signal is traced to Vetelsen's house . When the police raid it, they find Vetelsen dead of a shotgun blast to the head, along with the remains of Britte and another woman named Hegen Dahl . </P> <P> Katrine seduces Stop at a fundraiser event, and he asks her to wait in his hotel room . She sets a trap for him inside, but is attacked and drugged by a masked figure who severs her right finger and uses it to unlock the biometric security measures on her work tablet, wiping all the data from it . The next morning, Harry sees the impression of a snowman atop his snow - covered car, and inside finds Katrine's corpse in the driver's seat . </P> <P> Rakel tells Harry that Oleg has run away after Harry missed a school camping trip in which he was supposed to have joined him . Oleg stays at a friend's house, and when Rakel arrives to tell Harry the two kiss and almost have sex . Mathias calls to tell Rakel that he is picking up Oleg to take him home . Upon returning home, Mathias drugs and ties up Rakel, then does likewise to Oleg, taking both of them to a cottage in Telemark . Harry tracks him down, where he has Rakel and Oleg hostage with the cutter to Rakel's throat . Mathias is revealed as the boy at the start of the film, who grew to hate his mother because she did not want him to know who his real father was . Harry attacks Mathias and manages to get the cutter off of Rakel's neck, losing a finger in the process . Mathias escapes and, implored by Rakel, Harry gives pursuit, chasing Mathias onto the ice . Mathias manages to shoot Harry, but the ice beneath his feet suddenly cracks and breaks apart, dropping him into the water below and dragging him under the current to his death . </P> <P> After having his injuries treated, Harry returns to the police precinct, and volunteers for a new homicide case . </P>

Who was the killer in the movie snowman