The evil or insanity that filled James Holmes is easier to understand, in the sense that both have always stalked humanity. An especially virulent modern version is the antisocial man in early adulthood, the “loner” who turns mass murderer: Cho Seung-Hui at Virginia Tech, Jared Lee Loughner in Tucson, Anders Breivik in Norway, and now it seems a neuroscience student in a Denver suburb who police say identified himself as an arch-villain from a comic book-movie series.
Their killing sprees were not the result of lax gun laws or some profound societal ill. In an America with 200 million guns in circulation, an evil mind will find a way to get weapons of mayhem. If not guns, perhaps it would be bombs, or poison of some kind.
The much harder question is how a free society protects itself from a twisted mind. Families, educators and medical professionals need to be aware of the behavior that might signal psychotic breaks of the kind that tormented Loughner. In the case of Breivik, simple evil seems to suffice as an explanation.