Mandate that all facilities labeled, "gun free zone" have those labels removed in an attempt to eliminate potential killing grounds for predatory and sociopathic behavior.
Facilities marked with "gun free zone" labeling are a clear signal and invitation to predators and the like who wish to maximize destruction to human life through the inhumane action of unleashing firearms in public facilities with the knowledge that there will be no one available in the immediate area to fight back.
A startling number of mass murders all share this same trend, of attackers preying on those they quite clearly discern will not be able to protect themselves.