No solution, because there is nothing wrong from the gun angle. That is the issue.
Well, I wouldn't entirely agree with that.
Guns may not be the cause, but given how prominent they are in these shootings you can't say that there is no problem from the gun angle.
If there were equal numbers of mass-killings that included cars, molotov cocktails, baseball bats, farmyard machinery, etc then, yes you could argue that this has nothing to do with guns.
Anyhow, that is somewhat beside the point.
I will repeat what I said earlier: Talking does not automatically equate to negotiating. It does however widen the understanding of boths sides of the equation as well as those in the middle...
But it seems some don't even want to do that. In the meantime the problem will continue.