The Psycho Before Christmas by Michelle Hercules

Everyone thinks I’m the perfect daughter, a model student, and the star of the track team. But when an asshole hurts me, he’ll find out I have a darker side.
Then my plan of retaliation is foiled by Killer Santa, a psychopath who offed my ex before I could.
I spent a year hating him for denying me my revenge. I couldn’t have foreseen that the killer who terrorized our hometown days before Christmas was none other than my stepbrother, a sinfully gorgeous pain in my ass.
I hadn’t seen him since we left for colleges on opposite sides of the country. Now we’re back under the same roof, and all the feelings I suppressed return with a vengeance. Eric is my only weakness.
But it turns out we’re not the only monsters in town. Someone is hunting us, and it’s kill or be killed.
Sounds like a good Christmas to me.