As it turns out just about everything you may have been told about mass homicides in the United States is wrong. This article at The Conversation from researcher Christopher J. Ferguson may cast a little light on the subject. The perpetrators of mass homicides are distributed by race at roughly their proportions in the population and most are not male white supremacists:
Hateful people tend to be attracted to hateful ideologies. Some shootings, such as the 2016 shooting of police officers in Dallas, were reportedly motivated by anti-white hatred. Other shooters, such as the 2015 San Bernardino husband and wife perpetrator team, have espoused other hateful ideas such as radical Islam.
Most mass homicide perpetrators don’t proclaim any allegiance to a particular ideology at all.
Importantly, the prevalence of mass homicides is not increasing in the United States:
To be sure, the U.S. has experienced many mass homicides. Even stability might be depressing given that rates of other violent crimes have declined precipitously in the U.S. over the past 25 years. Why mass homicides have stayed stagnant while other homicides have plummeted in frequency is a question worth asking.
Nonetheless, it does not appear that the U.S. is awash in an epidemic of such crimes, at least comparing to previous decades going back to the 1970s.
Additionally, the United States does not have more mass homicides relative to the size of its population than quite a number of reasonably peaceful countries including Norway, Switzerland, and France.
In my view the causes of mass homicide are multifactorial including the frequent depiction of violence in the society tending to inure people to violence, the reporting of violence inuring people to violence, mental illness, the availability of high-powered firearms, other societal stresses, boredom, and any number of other factors.
The horrific nature of mass homicides makes it a fruitful vehicle for opportunistic political attacks but, as the author of the article notes, let’s not confuse the myths with the reality. Attacking the myths will do little or nothing to curb the reality.