One topic not being discussed here, aside from the numerous comments within the Obama administration regarding 'tragedies', and "not letting a good one go to waste," is the largely spread and widely accepted use in this country of SRIs or saretonin reuptake inhibitors. Nearly every person who has carried out these mass shootings in the last 25 years, has been on one form of them or another. When you mess with your own body chemistry, there are invariably going to be dire consequences. For most people it is an impairment of regular sensory function. Be that an inability to focus, feel, comprehend, etc. But for a select few, (and i use the term 'select' heavily), it results in a cataclysmic collapse, and violent response to said collapse.