Neuhart doesn't assault the women, his motive seemingly being simply to murder them. He uses stolen cars, which he abandons after the crime. And he writes little missives to the Gendarmerie, where he works, anonymously explaining his actions. He is clearly mentally disturbed, and when he starts a relationship with the young woman who does his laundry, Sophie, one fears the worst. But he seems to have feelings for her and his conflicted emotions are clearly on display.
Eventually he takes a risk too far, the police already being convinced that the suspect may be one of their own. The story is based on the novel Un assassin au-dessus de tout soupçon (An assassin above all suspicion) by Yvan Stefanovitch.