What kind of mass murderer is likely to die in the act, and why should we care?

There's a striking fact about mass murderers – an extremely high percentage (around 30 per cent) of them die in the act, either by suicide or because of deadly police force. Of course, only a saint would likely be moved to feel sympathy by this statistic, but a new paper digs into the reasons behind it, in the hope that doing so could help prevent future killings.

The formal definition for a mass murderer, as opposed to a serial killer, is someone who kills four or more people in the same act, "with no distinctive time period between the murders". This includes religiously inspired suicidal bombers, family killers (where one family member murders his or her partner and their children), and rampaging school shooters.

Researcher Adam Lankford at the University of Alabama (author of The Myth of Martyrdom) hired a crack team of investigative journalists to identify all the mass murders committed in the US between 2006 and 2014. The team mined media reports, FBI records and local police reports to find details of 242 cases of mass murder. Averaging 4.9 victims, and with over 90 per cent of the perpetrators being male, the crimes were coded according to several basic features such as killing type and age of offender, allowing Lankford to establish whether there was anything distinctive about the 31 per cent of mass murderers who died in the act (80 per cent of whom died by suicide) compared with those who survived.

Gender wasn't a relevant factor, but older mass murderers were more likely to die, as were killers who operated alone (48 per cent of those who lived had a co-offender compared with just 5 per cent of those who died). Mass murderers who died also tended to kill more victims (an average of 5.5. versus 4.6 victims among the surviving killers). Regarding types of mass murder, family killers were the mostly likely to end up dead (61.7 per cent), followed by public killers (i.e. rampage shooters and such like; 28.7 per cent), perpetrators of miscellaneous mass murders (e.g. gangland killings or neighbour disputes; 5.3 per cent) and robbery-related mass killings (4.3 per cent).

Why should we care about these statistics? Lankford's thesis is that they support the notion that "suicidal motives play a major role in the behaviour of many mass murderers". He draws on the work of the nineteenth century French psychologist Émile Durkheim to suggest that many of the mass murderers effectively took their own and other people's lives either as an act of egoistic suicide, "whereby people who lack social connections and the moderating influences of others are more likely to spiral into suicidal despair"; or anomic suicide, in which "[the killer's] anger and actions may lack clear purpose or direction"; or altruistic suicide, "which is carried out by people who feel they are serving some greater good".

Lankford points to the parallel between suicide statistics for the US population as a whole (where suicide rates correlate with greater age) and the fact that older offenders were more likely to die – "it is interesting that despite the aberrational natures of their crimes, mass murderers seem to fit with these basic demographic trends," he says. He also notes the apparently powerful protective influence of a co-offender. "Even among this extremely violent minority of homicide offenders," he writes, "the presence and social influence of fellow offenders may be critical to preventing a self-orchestrated death."

Lankford acknowledges that the exceptionally high rate of suicidal deaths among family killers may seem to contradict Durkheim's writings on suicide (Durkheim said that the married person's family bonds would keep them stable). But Lankford argues that "in the case of many family killers, that connection has clearly been broken" – frequently because the murderer suspects infidelity or feels abandoned in some way by the family.

One of Lankford's most important messages is that a "side-benefit" of improved suicide prevention strategies is likely to be a reduction in the occurrences of mass murder. And he warns that just as high-profile (non-homicidal) suicide cases often prompt a temporary increase in suicide rates, "it appears that some recent mass murderers have been influenced and inspired by their knowledge of other highly publicised killers." One preventive strategy in this context, he says, is for the media to avoid glamorising mass murderers and to deter potential copycats by covering "… the more humiliating aspects of the killers' own deaths, such as the fact that their bowels often release and leave their body soaked in urine or faeces".

Further reading

Lankford, A. (2015). Mass murderers in the United States: predictors of offender deaths The Journal of Forensic Psychiatry & Psychology, 1-15 DOI: 10.1080/14789949.2015.1054858