In the aftermath of a mass shooting, hindsight kicks in quickly. Friends, acquaintances, colleagues, or teachers are often able to pinpoint moments where they realized something was wrong with the perpetrator, or simply felt uncomfortable. President Trump picked up on this idea of warning signs in a tweet Thursday morning, responding to the killing of 17 in Parkland, Florida, the day before:
So many signs that the Florida shooter was mentally disturbed, even expelled from school for bad and erratic behavior. Neighbors and classmates knew he was a big problem. Must always report such instances to authorities, again and again!— Donald J. Trump (@realDonaldTrump) February 15, 2018
With the prospects for changes to gun laws and regulations effectively frozen at the national level, the debate after shootings has often gravitated toward similar lines of discussion, often centered around mental health. Since there’s little prospect of regulating the weapons used in the shootings, the focus is on intervening before the point when someone opens fire. Yet this line of thinking is flawed, both practically and philosophically.
First, it depends heavily on retrospect. But things that seem like obvious warning signs after the fact may have just seemed weird beforehand. (People rarely really expect anyone to become a mass shooter, since statistically such attacks are vanishingly rare.) Conversely, there are thousands of people, and especially young men, who might set off warning bells—they act strangely, they’re obsessed with weapons, they engage in various anti-social behaviors—but who will never take a gun to school and open fire.