The first port of call is usually to look at beliefs, but the trouble with beliefs is that they do not always reflect behavior, especially if the behavior involves murder. Even extreme ideologies that promote greater intrinsic value over the life of one group of people than another, such as white supremacy or any religion that promotes an infidel/believer dynamic, would not permit most people to follow through with an act of killing.
This does not mean the adherents to such belief systems would not revel in the death of certain individuals or turn a blind eye, but in terms of carrying out the act, the belief alone does not seem enough.
The potency of a belief (it’s ability to affect behavior) may be determined by the dominant parent culture. If the parent culture endorses or encourages personal beliefs, then the likelihood of them affecting behavior are high, provided of course that the individual agrees with the parent culture. The beliefs and values that make up the parent culture are less likely to come with penalties, and maybe even carry a reward. Theoretically, murder of citizens by citizens in the United States carries very heavy penalties, and so even if a person believes that the murder of some individuals is permissible, the desire to avoid punishment will probably act as a deterrent (unless they’re a psychopath – see bottom of post).
So what else could be going on beyond beliefs?
There are two things that the shootings in Aurora and Milwaukee have in common.
Firstly, the gunmen both experienced potentially life-changing failure. James Holmes, the gunman in Aurora, was a PhD candidate in the Anschutz Medical Center (part of the University of Colorado) and supported by a federal grant. Holmes had also been seeing a psychiatrist, although the reason for his visits have not been made public. As Holmes failed an oral exam, it is probably safe to assume he had been anticipating failure or suffered a great deal of anxiety about the exam. This stress and anxiety was no doubt exacerbated by the pressure of having a federal grant and the subsequent need to maintain a high level of performance. If his visit to the psychiatrist was for something beyond the anxiety caused by these factors, then the potential state of his mental health becomes even worse.
Wade Michael Page, who killed six individuals at the Sikh temple in Milwaukee, had also suffered potentially life changing failure. He had been demoted and discharged from the US Army and was ineligible to be re-enlisted. After spending six years in the army he was suddenly forced to find another job and no doubt felt a great deal of shame / embarrassment / anger over the discharge (possibly even anger at the US – the parent culture). He was clearly having problems with alcohol, too, as he was disciplined for being drunk on duty and going AWOL.
Both Holmes and Wade, who were both showing signs of mental illness, were forced to shape a different future for themselves from already investing a lot in their current career path.
Secondly, both shooters seemed to treat their massacre as a means to an end. Holmes went quietly and respectfully with the police, and Wade fired at policemen and ended up being shot and killed. Neither one of them showed any regard for a future (one they had been forced to re-shape), and seemed to embrace the US justice system or death, respectively. A terminal outlook of the immediate future can be used to rationalize anything, because one, it doesn’t require much effort or time for a depressed mind to conclude that life is pointless (meaning ALL acts have EQUAL value), and two, the deterrence of a parent culture no longer matters to the individual.
Another point to note about the killings, is that the gunmen clearly had no empathy or regard for life when they mercilessly shot members of the public. There are numerous explanations for this. Firstly, depression / anger / feelings of betrayal led to the shooters feeling like their own lives were not valued; this was then transferred to the victims. Secondly, the terminal end point was of greater value to the shooter than the lives of the victims. Thirdly, personal beliefs devalued the lives of the victims. I think the last reason here was probably apparent with Page, who appears to have been involved with White Supremacism.
It is also worth mentioning the act of suicide, because if the shooters both had terminal goals, then why not just kill themselves without taking the lives of anyone else? I think it is obvious that both shooters wanted to make some kind of violent statement before the terminal end as a manifestation of their anger and as a desire to be taken seriously (something they felt could have been missing before they were rejected).
It is worth taking a brief moment to consider psychopathy. In my opinion, most shooting sprees are not carried out by psychopaths. Killing sprees are not the M.O. of the psychopath. Despite the disregard for the lives of others, psychopaths do not demonstrate the belief in a terminal end point, in fact they love abusing and manipulating others, and would probably prefer to keep doing it and keep getting away it. Psychopaths would only go on a killing spree, therefore, if it was endorsed by the parent culture – which has no doubt happened in various military groups/regimes throughout history.
I would like to point out that attempting to understand why a person kills is not the same as finding excuses or defenses for these despicable acts. But it must be realized that culture and the environment are profoundly powerful forces in shaping minds, and so before disposing of people and subjecting them to an uncertain/unstable future, perhaps an effort should be made to assist them through the transition?