David: You did the right thing. I don't blame you.
David: I'm a soldier, man. I like guns.
David: Those kids at school, are they bigger than you?
Luke Peterson: Yeah.
David: Then bring a knife to school. If they take it off you and beat you up, you go around their houses at night and burn them down with their families inside. What's the worst they can do?
Luke Peterson: Yeah... Umm... Okay.
David: Do you want advice, Luke?
Luke Peterson: Sure.
David: Never let anyone pick on you.
David: Otherwise, you'll carry it with you the rest of your life.
Answer: The officer knew that David would methodically clean after himself.