There are many types of murder including single death, serial and mass. Single death homicides are, as the name implies, a one time event. Serial murder is one victim at a time repeated over and over, with a separation between the murders, described as separate occasions with a cooling-off period in between.
The FBI defines mass murder as “Four or more murders occurring during the same incident, with no distinctive time period between the murders. These events typically involve a single location, where the killer murdered a number of victims in an ongoing incident." The Colorado shooting by James Holmes was a classic mass murder.
According to the 2010 FBI crime data, since 1980, single victim killings have dropped by more than 40 percent. While that's very good news, there's a new sobering trend: Mass murders are on the rise. This New York Times article researched the frequency of mass murders. It found during the 20th century there were about one to two mass murders per decade until 1980. Then for no apparent reason they spiked, with nine during the 1980s and 11 in the 1990s. Since the year 2000 there have been at least 26, including the massacre in Aurora, Colorado.
There are common motives in single victim murders. For male murderers these includes revenge, power, money and rage. For the female killer, love is usually the motive, whether it involves a child, boyfriend, husband, or an ex. For a single death, the murder is typically commited by someone who knows the victim. For the serial killer, the majority of victims are strangers. Also, the serial killer's motives, which are for multiple reasons, evolve throughout the series of crimes and often relate to a thrill (sexual or otherwise). This is similar to the thrill of the hunt and involves scouting for a victim, planning the attack, the stalk and eventually the killing.
The mass murder motive on the other hand is very different. While they have their own perceived reasons for killing these rarely make logical sense. As for demographics, the mass murderer is typically a white male, a loner, has a college degree or some college, from a relatively stable background and from an upper-middle to middle class family. They often aspire to more than they can handle, then form a hatred and blame others if they fail. Also, they are much more likely to suffer from a mental illness, specifically some type of psychosis.
The number one predictor of violence by far is alcohol and/or drug abuse. Severe mental illness in and of itself was not a predictor. A 1988 study in the Archives of General Psychiatry found that patients discharged from psychiatric facilities who did not abuse alcohol or illegal drugs had a rate of violence no different than that of their neighbors in the community.
However, the study, Violence and Severe Mental Illness: The Effects of Substance Abuse and Nonadherence to Medication, found that when when a mentally ill individual was not medicated and abused either alcohol or drugs, there was a significant increase in serious and violent acts. So clearly, early psychiatric assessments, medication treatment and preventing substance abuse, will go a long way to preventing violence in general.
As for gun control, the studies are all over the map. From anecdotal reports to definitive studies, from the NRA to the Brady Campaign, each side uses mass murder to further their cause. I won’t bother to give examples of the numerous reports, studies and opinions. However, the gun laws are relatively unchanged over the last few decades. Over this time period, some states have stricter gun laws while others have become more relaxed. Regardless of how you feel about gun control in general, there is no correlation between gun control strictness and mass murder. For more see: Gun Control or Carry Permits Won't Stop Mass Murder.
So, what is fueling this spike in mass murder? What is different today versus 50 years ago that can explain 26 mass murders from 2000 to 2012, as opposed to one or two per decade from 1900 to 1980? First, there is no study I’m aware of that looks at this specifically. There are studies that look at violence and media exposure to violence, in particular The Role of Media Violence in Violent Behavior, which concludes that “Media violence poses a threat to public health inasmuch as it leads to an increase in real-world violence and aggression.” This is looking primarily at self reports and laboratory results with respect to the potential for aggression, which doesn’t necessarily translate into the real world. And again, this is a tough argument to accept in general with real world violence on the decline in the face of ever more violent TV, movies, song lyrics, internet and video games.
So, is there anything we can conclude from all of this? One question that needs to be addressed is whether the virtual violence that predominates our culture, while not affecting the general population, is affecting a small subset of younger individuals with a mental illness, who are not medicated or involved in any sort of treatment. Are they at a higher risk for becoming mass murderers? If so what can be done?
The first thing not to do, is to jump to a conclusion based on politics, a knee jerk reaction, a pet theory or your views about guns and/or gun control. The only logical conclusion at this point is that the single most important preventative measure is the early recognition and treatment of severe mental illness in general, and psychosis in particular. That coupled with the importance of keeping a psychiatric patient off alcohol and drugs is all we have until further research is completed.