This is an interesting psychological analysis of mass shooters. Here is a part of it
http://www.whywesuffer.com/the-psychology-behind-mass-shootings/
"While some mass shooters are psychotic or schizophrenic, only about
five percent of violence in the United States can be attributed to people with mental illness. The rate of mental illness is higher—an estimated 20 percent—among rampage or serial killers. Most of the mass murders didn’t qualify for any specific psychiatric disorder, according to strict criteria. These individuals—often working-class men who had been jilted, fired, and felt humiliated, or youths who felt rejected and despised—lived next door to neighbors who never imagined them capable of such crimes.
We would like to believe that the behavior of the shooters is foreign to human nature, not something intrinsic in our psyche. Or we say that a gun-worshipping culture is to blame. Yet might there be another factor, some common element at the heart of human nature, to account in part for these horrendous events?
Let’s start by examining a profile that fits many mass shooters. These murderers are often quite intelligent, yet through acute self-centeredness they are likely to be socially awkward or inept. They crave notice and fame to compensate for how deeply they dismiss their own value and feel like nobodies. They also lack empathy and have little or no affect, a condition that relates to the indifference or disdain they have for their own existence.
Negative emotions accumulate inside them, producing bitterness, anger, despair, and, finally, rage. Their rage, even when hidden from others, produces a third-rate sense of power that covers up their emotional entanglement in hopelessness and passivity. They crave power because they feel so powerless, yet in their dark negativity they can express only negative, destructive power. They seek death because they feel so powerfully overwhelmed by life.
Because their weak self-regulation compels them to continually recycle negative emotions, they hold on to grudges. These grudges and grievances accumulate in them, giving them a feeling of substance, a place of being to which they cling in the chaos of their inner conflict.
The killer-to-be has also passively allowed himself to plunge so deeply into self-abandonment and self-hatred—meaning his aggressive rejection of all that is good or decent in him—that, like a drowning person, he gasps for the one last “breath” of the only power now available to him, which is to do evil.
An additional factor shapes these menacing time-bombs. These killers-to-be have acquired a fervent interest in guns. Influenced by others, they passively elevate the gun or the rifle to level of a fetish. In another time and place, they’re the kind of people who might have joined a cult. For a troubled individual who is drowning in negativity, to adore guns is to worship death.
From this we can assume that the murderous instincts of rampage shooters originate from profound inner weakness and emotional conflict in their psyche. Their aggression, in part, is based on their reaction to their overflowing negative emotions and their resulting lack of self-regulation. By way of comparison, many everyday people have considerable deposits of anger, cynicism, and bitterness. They hold on to this negativity for dear life. Convinced that their bitterness is justified by the alleged cruelty or insensitivity of others, they express various levels of malice toward others. This is the key point: We have to learn and understand that our bitterness is not due to the malice of others. Rather,
the bitterness and rage we may experience is a cover-up for our willingness to indulge in feeling victimized in some manner or other. If we don’t understand this, then the difference between us and rampage shooters is just a matter of degree.
To heed Jung’s warning, we must grow our consciousness. This inner progress would enable parents, teachers, clergy, and others to become more insightful about the emotional state of others and more confident about initiating some form of intervention. As well, potential killers will likely moderate their deadly instincts when they are surrounded by more conscious people, exposed to better psychological knowledge, and made through saner weapons regulation to understand that the death instinct, easily spawned where weapons are sanctified, is a social taboo. "