Statistically, the mentally ill are usually the victims of crimes and not the perpetrators.
http://mentalillnesspolicy.org/conse...imization.html
http://www.sciencedaily.com/releases...0225101639.htm
If there were indicators about who might go on a shooting spree, then I would be for evaluations to stop such actions. Life is never that simple though nor, of course, is the human mind.