"My Bad"

Tori is the neighborhood killer that nobody knows about. She sees the true faces of the evil men and women in town. Or so she thinks. She lives her life thinking she's a normal teenager, going to school, getting good grades, goes to parties. Everything every normal girl does, right?
One night, Tori ventures her way into the wrong party. It lasts a little too long and before the poor kids at the party know it, the mask is being pulled on and the killer is whispering "My Bad."

Is Tori special or is her mind simply playing an evil trick on her?