The math doesn't say that - the 120 per 100 figure is misleading: obviously everyone doesn't own a gun. About 22% of people report owning a gun. So yes, a high figure, but the chance of someone owning a gun AND currently carrying it brings that number down a bit. I do agree that it's still quite a dangerous situation regardless.
Well then let's run the numbers: which math are you talking about, the number of guns? My question stands, then. After that, where is the line that changes the dynamic "entirely?"