There appears to be a triad of factors that sets these killers apart. The first is that they are generally struggling with mental health problems that have produced their desire to die. The specific psychiatric diagnoses vary widely, and include everything from clinical depression and post-traumatic stress disorder to schizophrenia and others forms of psychosis. The suicide rate was 12.4 per 100,000 people in the United States in 2010 (the highest in 15 years). Suicide is relatively rare, but it is rarer still in most Muslim countries. This is a very limited pool from which most suicide terrorists and rampage shooters come.

The second factor is a deep sense of victimization and belief that the killer’s life has been ruined by someone else, who has bullied, oppressed or persecuted him. Not surprisingly, the presence of mental illness can inflame these beliefs, leading perpetrators to have irrational and exaggerated perceptions of their own victimization. It makes little difference whether the perceived victimizer is an enemy government (in the case of suicide terrorists) or their boss, co-workers, fellow students or family members (in the case of rampage shooters)…

The third factor is the desire to acquire fame and glory through killing.