This is perfect method of advertisement that the zone is a gun free zone giving shooters perfect opportunity to screw somebody else and run.
If there is no gun free zone, the shooters will be likely unable to find opportunity to commit and run.
It does ponder me on wondering why Americans have not notice the history on prohibitions. We had alcohol prohibition and the problems only gets worse until they dropped the ban. Also with drug prohibition going on, more and more new dangerously designer drugs getting widely available sending suckers to emergency room with their potential final destination at graveyard. When one decided to prohibit guns, there will be more negative consequences going to happen regardless.
I believe the only way to relieve these kind of problem is, expect it to happen again regardless, and allow truly law abiding citizen CCW. Once there is enough CCW law abide citizen exists, these cowards aren't going to risk their lives.
I personally feel more safer around people who have guns than being around nobody that got gun.