For my first true crime story, where we know who did it (although the why might be a little fuzzy), I decided to go with someone you probably haven't heard of.... And is a woman.
Male serial killers get a lot of attention, but Magdalena ended up with the title "High Priestess of Blood." The lesson here is: anyone can be a serial killer. And I would probably like to add the caveat that anyone can be a serial killer, especially when they're involved in a cult.