The over-medicated may be right. The recent shooting at Fort Hood in Texas was in a "gun-free" zone but a soldier who had never been in combat was still on prescription medication for psychiatric issues related to combat zone trauma. As long as psychiatry remains trapped in the symptom-based world of the past, it is going to be the case that someone who complains enough will get a prescription.
But a group of scholars in Violence and Gender instead say we should be looking at what clothes they wear - and that they are males. Brian Van Brunt, EdD and W. Scott Lewis of The NCHERM Group, LLC law firm that sues colleges when safety issues happen, suggest reasons why persons who commit mass shootings are drawn to dark popular culture imagery, how these cultural factors may contribute to the violence, and what risk factors could be useful to law enforcement and behavioral investigation teams seeking to identify individuals who might be preparing for an attack.
The line between being a SWAT team member and wanting to look like a SWAT team member is apparently fluid and the authors engage in a great deal of speculation about God and monsters. Along with dark imagery (Neo in The Matrix, Ring Wraiths in The Lord Of The Rings) the authors say sociopaths also leave behind 'legacy tokens' (Batman's batarang) and they cite the instance of Norway's Anders Breivik, who killed 77 and injured more than 300 in 2011 and had prepared a 1500-page manifesto.
Northern Illinois University shooter Steven Kazmierczak's tattoos. doi:10.1089/vio.2014.0003
Light and darkness as metaphors for good and evil have been cultural staples for centuries but invoking Carl Jung dooms us to European culture pretenses. They note the Canadian shooter from 2006 who considered himself a Death Knight - but the imagery did not create the problem so correlating tattoos to possible violence is no more valid than correlating organic food to autism - though curves show it.
Objectification is common, people who sociopathy lack empathy, that is true, but plenty of people without Batman pretensions commit crimes. Pekka-Eric Auvinen of Finland killed 8 people. Blame for that was not placed on Finland's gun culture or Batman, it was placed on Finland's darkness, cold temperature and its overall anti-science culture.
Sociologically, advocates map events to their beliefs, so if you believe tattoos and Johnny Cash outfits are scary, you may find mass murderers in lots of places, even though they don't exist.
Costuming, Misogyny, and Objectification as Risk Factors in Targeted Violence
Van Brunt, Brian and Lewis, W. Scott. Violence and Gender. April 2 2014 doi:10.1089/vio.2014.0003