Angry kid with a knife
The scrawny ginger nerdy kid with the slow burning explosive temper. (stealing a page from our higschool here) In middle school, when he was being harassed by another kid he stabbed a pencil clean through the other kids hand. Since then people have been more respectful, or at least cautious, around him. That is except for the jocks who have made a sort of game pushing him almost to the point of losing it and then backing off. Laughing and cracking jokes in their dumb jock way at how red his face gets the more angry he becomes.
As for knowing he has a knife. Well, one of the jocks in the process of teasing him emptied his bookbag on the floor in the hallway of school. When he did this a fuckhuge hunting knife rattled out onto the floor. He managed to get rid of it and leave school grounds before anyone in a position of authority could arrive on the scene. But now everyone walks on eggshells around him and the Principal has his eye on him.