Luke is a serial killer, an assassin. narcissistic, cold, sadistic.

you were at a party and you saw him kill someone

I was killing someone again. After punching his head and stabbing his heart with the knife, I took my bloody hands off the body. At that moment I saw a girl looking at me. My eyes widened, but then a huge grin appeared on my face. I walked towards the girl and started chasing her

"You bitch! Of course I'll catch you! You don't even have to run away!"