'Undisturbed' is doing a bit of lifting there. The same could be said of a person, generally speaking. Leave most people in a room, they won't hurt anyone either. It's just a matter of what circumstances make each dangerous. If you put bullets in a room and set the room on fire, they act as little bombs. If you do that with a person, it makes them less dangerous, because they're dead. If you put a person in solitary confinement for years on end, they'll come out mentally disturbed, and possibly violent. Do the same with a bullet, and it comes out presenting the same hazards as when it went in.