Read a good article from a pro about the correlation of mass murdering shooters and their drug use (prescription and non). Anabolic steroids are known to cause uncontrolled rage, when combined with Ephedrine and Caffiene (as in most "Energy Drinks") the effect is obviously obvious. Anti-depressants are freely prescribed, and cause a sort-of detached view of reality by their very nature. Chronic, heavy Cannabis users and Alcholics impose their own impulsive issues. ALL of the known shooters in the last few decades were so impaired to some degree.
They ALL have one other thing in common, they are PSYCHOTIC and PARANOID, likely hearing inner voices that don't stop. The last 2 Monsters that rampaged (Oregon and Newton) had one more thing in common, Lanza shot himself upon hearing Police sirens approaching, the Mall Shooter shot himself after the by-stander drew down on him. They are cowards, and want to maintain control to the very end.
My idea (and you saw it here 1st) is PSY-OPs, done covertly of course, with NO media unveiling or ANY public mention to decrease it's potential to feed on the Shooter's paranoid psychosis. Imagine loudspeakers positioned around the perimeter, programed to simulate approaching Police sirens, getting ever louder (from differing directions), finally schreeching to a stop, doors slamming, feet running, loud speakers blaring, even interior speakers with the sound of doors and glass breaking. Gives me chills just thinking about it ... ! This is simple and cheaply done with todays electronics and battery back-up. Remote, inconspicuous key operated panels in all areas provide instant activation by key personnel.
If someone patents this after reading this and makes $$$, don't forget to send my royalty check, heh, heh.