I won't say "The guns are the problem", but the argument you use is against your thesis.

Without Guns, like the school attacks in China prove, there is far less victims. For something like 10 attacks, there is "only" 21 death.

Without Guns, the real problem, the lack of treatment of mentally ill, would cause far less victims.

I agree, guns are not the problem, but guns have a part to play in the problem... at least on the number of death. Guns are MADE to kill, and they do it better than a knife. You could argu : "But a bomb could kill as much.", but until america don't "promote" bombs as much as much as the guns are "promoted", mentally ill won't think about using a bomb and they won't already have one in there hands because "it's their right"

I think the equation is more something like : X=Y*Z Where : X is "probability of random violence" Y is "access to guns and/or any other tool to kill" Z is "mental illness" I think that the real problem is with Z, and that's where most efforts should be put. But, that doesn't mean that reducing Y won't have any impact on X. One thing for sure it will help at having less dead victims.