The Killer Is Not Alone(1975)

Original title: El asesino no está solo

Julio, an only child belonging to a wealthy family, murders a prostitute who tries to seduce him. He, in childhood, suffered severe trauma and this causes serious problems with women. Because of this, runs away and stays in a boarding house in Madrid, where he meets Monica, the daughter of the owner, who maintains relationships that seek to build on for help in their desperate situation. As his obsession for killing is increasing.