One 'difference', Ebbie, is that anyone trying to run amok with a knife in a crowded mall would not get very far or have the chance to stab many people before being stopped & overpowered. With a gun, judging by #s of deaths involved in your innumerable instances of such, and our very few copycat ones like Hungerford & Dunblane*, that is a whole lot more difficult.

≈M

*Honestly can't think of any others