Serial Killer: Ted Bundy The most distinguishing factor of a serial killer is multiple victims, generally four or more victims. A serial killer will continue killing until he is made to stop. Serial killers differ from mass murders. A mass murder may open fire in a bank and kill several people, making him a mass murderer. A serial murderer does not kill several people in a matter of hours only. The killer goes through phases. He claims a victim, has a cooling off period, and then claims another victim in a week or month. A serial killer may even wait years before claiming another victim. The killers go through a cooli