Good question.
 

The "fuck" is that everyone is scared shitless whether they want to admit it or not. The kid who left the "there's-a-bomb" is a wise ass. A scared shitless wise ass. He (or maybe even a she) thinks he's just getting everyone cranked up & classes are disrupted & he doesn't give one wifty damn because we're all gonna be blown to smithereens anyway, sooner or later. Maybe he can even see little globs of body parts flying around & then settling into the crater that was once his school. And there he ..... or parts that were once he ..... embedded for eternity.
Lesson learned? You can't get out of being in school ....ever.