I don't think it's anything to do with terrorism, or even craziness. I think it's to do with boredom, disillusionment and restlessness that eventually leads to the narrator having some kind of 'fuck this shit' breakdown. For me, it's always come off as more metaphorical than Bang Bang. I have days when I 'want to lead a long trail of destruction, and mow down any bullshit that confronts' me, but that's a million miles away from the disturbing wish for fame for mass murder that's contained in Bang Bang.