A Science for Everyone

Mass Shootings and Jumping to Conclusions

I noticed reports of a supermarket shooting in Colorado – at first the perp was a white supremacist, then an ISIS influenced domestic terrorist, and, most recently a Syrian-born immigrant with mental health issues.  There’s a challenge when you need to get a story into print quickly, and the first story often changes.

Mass shootings have been a topic for research, and data is available online.  I’ll refer to  Emma Friden’s study in the Journal of Interpersonal Violence – it can be accessed at here.


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Excerpts show some of the challenges in dealing with the topic.  Friden begins by separating these into 3 categories- familial, public and felony. 

The public area mass shootings are what we tend to think of most frequently, but her chart shows that the most common mass shootings are familial, when someone loses it and murders their family.  Felony mass shootings refer to the shootings that occur during a felony, often to get rid of witnesses.  Her descriptive statistics are below.

Sometimes the interesting part of the statistics is what isn’t there – in this case, there is no category for sex of the offender.  I’m not certain, but I suspect it’s all male in the data set. 

The second set of numbers that set off a mental bell was for immigrant offenders.  It seems disproportionately high – though I’ll need to use Census data to check.  I like seeing data – it makes things much more understandable.

I can’t make a good excerpt of the paragraph that sums up her work, so I’ll ask you to read the whole thing: “These findings are broadly consistent with prior research, as familicides are primarily differentiated by victim characteristics, felony killings by offender characteristics, and public massacres by incident characteristics. Specifically, offender and victim characteristics distinguish family from felony murder; victim and incident characteristics distinguish family from public killings; and offender and incident characteristics distinguish felony from public massacres. However, only a few traits consistently differentiate each type from all others: Family killers target children and other family members of the same race, felony offenders rarely perish after their crimes, and public attackers use guns to injure as many victims as possible. More interesting than these anticipated differences among the three groups are the traits that do not significantly vary, contrary to traditional assumptions. Although previous studies have suggested that family killers are older than their counterparts, suffer from financial stressors, and tend to target more female victims, none of these predictors could significantly differentiate familicide from the other two types when all other variables were accounted for in the model. Similarly, felony killers are no more likely to be Black over White in comparison with family killers, and no more likely to have a violent criminal record than either of the other categories. Far from mentally ill pseudo-commandos, public killers were just as likely to have been treated for mental illness or have military experience as other assailants.”

Usually, criminology isn’t my thing – generally, crime is defined socially and is kind of a moving target.  I’ve watched marijuana go from felony to legal, varying by time and state line.  This study deals with something that is consistently considered a crime, and categories that are definitive.  Her article is definitely worth reading.