Well, when you think about it, these particular shootings get mass media attention because they are mass shootings, not because they are the most common types of crimes being committed. In actuality, these mass shootings are still pretty rare; they just receive much more air time because they are so horrendous in nature. It does appear that most of the time, the individuals committing such mass shootings do end up having a pretty extensive history of mental illness, sometimes exacerbated by drug use which seems to be a very dangerous combo for the most seriously mentally ill. Secondary to mental illness seems to come terrorism, and often some combination of the two.