Cause and effect. Let's do this. Human tendency for uninformed irrational behaviour or an erratic tendency to violent actions with the action assisted by a rapidly destructive piece of metal resulting in mass death. Take away a gun and you still have irrational and erratic behaviour but there is no mass death. Imagine this: If I point my trigger finger at you and simulate pulling a trigger did I shoot you? No. Now, if I point my gun at you and pull my trigger finger did my gun shoot you? Yes. Same action. Different result. Impact difference maker...a gun.