There are many relevant previous threads, especially valuable IMO are:

NYPD: Active Shooter - Recommendations and Analysis for Risk Mitigation, January 2011:http://council.smallwarsjournal.com/...ad.php?t=12366

Arizona Rep. Giffords' shooter called very disturbed, September 2011:http://council.smallwarsjournal.com/...ad.php?t=12229