Maniac (2012) on Netflix

The restorer Frank is the owner of a mannequin store that belonged to his mother. Frank was abused by his mother when he was a child and now he is a psychopath serial-killer with a fetish for scalps. When he meets the French photographer Anna, she loves his work of restoration of mannequins and they become friends. Anna borrows mannequins to an exhibition that she is promoting and Frank helps her. Franks goes to the opening night and stalks and kills Anna's agent Rita (Jan Broberg). Anna calls Frank to tell what happened to Rita and he goes to her apartment. Soon she suspects that Frank might be a serial-killer, but he is in her apartment.