The twist is that you're actually a very mentally ill serial killer, so your victims look like zombies. Because you hate zombies so much, you feel the urge to kill them in a long, drawn-out manner - hence the mandatory order for limb removal
Such a deep and moving story. Maybe you should submit this to the IGDA or even get Anita Sarkeesian to do a piece on the empowered female main character (tranny Antonia Banderas)