Protecting children from gun violence in K-12 schools means facing two realities: the roots of violent intent and the destructive capacity of firearms. In a recent study published in Criminology, my colleagues (Cory Schnell, Steve Chermak, and Josh Freilich) and I revisited a decades-old question: do firearms or motivations to kill drive mortality during school shooting assaults? The answer was striking. Lethal intent mattered—but so did the weapon. Of the incidents we studied, when a shooter used a higher-caliber gun, such as a .45 caliber versus a .22 caliber handgun, the chances of someone dying in the event increased even after controlling for the shooter’s background and, importantly, why they acted. In short, caliber counts. Encouragingly, there are concrete policy steps that can be considered and implemented to make it count less.
The Research Problem
Firearm incidents are now the leading cause of death among children and teens, and the need to systematically examine the factors leading to hundreds of injuries and deaths from shootings at America’s schools has never been greater.
For decades, criminologists and public health researchers have tried to untangle the mechanisms that make the difference between life and death during armed assaults. One theory, known as the instrumentality hypothesis, emphasizes the central role of weapon technology in shaping homicide.
Studies have long found strong associations between guns and lethality when compared to other weapons, such as knives or blunt tools. Deadlier weapons tend to produce the deadliest outcomes—and this holds true across different firearm types. In a landmark 2018 study in JAMA Network Open, leading scholars Anthony Braga and Phillip Cook discovered a clear correlation: using data from Boston Police Department investigative records, as firearm caliber and power increased during violent encounters, so too did the likelihood that injurious assaults became fatal. As the authors stated in a later article, “[g]uns do [in fact] kill people.”
But correlation is not the same as causation, and there are sound reasons to question the firearm-homicide link. For one, available evidence comes primarily from nonexperimental research studies (research that doesn’t involve controlling conditions or assigning people to groups), which opens the door to alternative explanations of outcomes. It is possible, for example, that individuals highly motivated to kill may simply choose the deadliest weapon available, or those individuals with preexisting hostile dispositions may escalate minor disputes into fatal encounters. If so, then intent and determination, not the firearm’s intrinsic power, would be the true drivers of lethality.
Criminology, for all its progress, has been slow to separate the decision to commit violence from the tools, like firearms, that make doing that harm possible. Certainly, there have been efforts to measure a person’s determination to kill alongside their weapon use, showing that firearms act as a force multiplier, increasing the chances of severe injury when they are deployed in criminal actions.
However, these earlier studies are limited, as they rely on incarcerated men recalling years later whether they meant to seriously wound their victim, raising concerns about accuracy, memory lapses, and self-serving bias. Furthermore, while prior studies of school shootings have examined both motivation and firearm use, none to our knowledge have directly tested the instrumentality hypothesis in this context.
Our Study
Against this backdrop, our study took a different head-to-head approach that was grounded in specific data. Using original data from The American School Shooting Study (TASSS), we were able to track both what school shooters did—concrete behaviors signaling specific intent to cause serious harm—and the firearms they carried, including size, caliber, and design. This dual focus allowed us to see just how human motivation and weaponry interacted to shape the odds of survival during injurious school shooting incidents.
Most school shooters in our study acted with lethal intent: nearly three-quarters (73 percent) opened fire with the goal of killing or seriously injuring someone. Fewer brandished firearms to defend themselves (21 percent), intimidate a person (7 percent), or for other reasons. Many of these decisions were calculated rather than impulsive (71 percent), and more than half occurred after someone provoked the shooter (57 percent). The largest group—about 44 percent of all cases—involved shooters who made preplanned and unprovoked decisions to kill, the clearest marker of murderous intent. School shootings perpetrated by these individuals were 18 percent more likely to result in death.
…the weapon’s lethality amplified the outcome regardless of the shooter’s mindset.
But intent was only part of the story. The firearms themselves mattered just as much, if not more. Using more powerful guns, measured by features like caliber (the diameter of the bullet) and muzzle velocity (speed at which a bullet leaves the firearm’s barrel), increased the probability of death by about 22 percent, even after accounting for intent and other relevant variables. In other words, the weapon’s lethality amplified the outcome regardless of the shooter’s mindset.
Access to firearms also shaped these events. Most shooters did not purchase their own weapons. Instead, 80 percent of shooters obtained the firearm they used through family, friends, or informal markets, suggesting that the power of the weapon often reflected availability, not careful selection by the shooter.
Put simply, who pulls the trigger is critically important, but so is what they carry in their hands.
Taken together, our results show that both intent and instrumentality matter. Moving from weaker intent with a low-powered gun to stronger intent with a high-powered gun nearly doubled the probability of death from about 39 percent to 77 percent. Put simply, who pulls the trigger is critically important, but so is what they carry in their hands.
What This Means for Public Policy
Our findings imply that a comprehensive approach to preventing firearm violence in schools should address both access to deadly weapons and the development of violent intent. Solving the school shooting problem likely will require policies that operate across multiple levels, from state legislation to school-based practices.
At the state level, child access prevention laws—which hold adults accountable for improperly storing firearms—have been shown to reduce a wide range of gun-related harms. Likewise, Extreme Risk Protection Orders (ERPOs) offer a promising, though understudied, tool. These civil orders allow authorities to temporarily remove firearms from individuals (or households when youth are involved) who pose a clear danger to themselves or others, limiting their ability to carry out attacks.
At the local level, schools can play a direct role through behavioral threat assessment and management. Our research showed that violent intent often develops gradually and is signaled through observable warning signs such as threats, sudden behavioral changes, or expressions of rage. Threat assessment teams are designed to identify these red flags early, evaluate the seriousness of the risk, and intervene with tailored plans of support. Rather than relying solely on punishment, this approach connects at-risk students with the care and services they need while enhancing overall school safety.
Overall, these strategies illustrate that no single intervention will be enough. Effective prevention requires a layered approach that reduces access to high-powered firearms, empowers authorities to act when risks are imminent, and equips schools to recognize and address troubling behaviors before they escalate to deadly ends.
ABOUT THE AUTHOR
Brent R. Klein is an affiliate scholar with the Regional Gun Violence Research Consortium and an assistant professor Department of Criminology & Criminal Justice at the University of South Carolina.