Even when law enforcement's response to an active shooter is flawless and entirely by the book, the attacker can still leave behind injuries or deaths. The Metro Nashville Police Department's officers were praised for quickly ending a mass shooting in April 2023 at a private parochial school. Officers responded in less than 15 minutes from the initial 911 call reporting an active shooter. Yet the community was still harmed by the deaths of the three staff members and three students. But just how did the attacker go undetected until that day? Is any attack unexpected? Research shows that people don't just become active shooters or attackers in a snap. Instead, it's a decision. "Right now, it seems like we're completely focused on the response to these incidents," said Joshua Shelton, a senior security specialist at FedEx in Atlanta. "The problem is...you can't do something until you hear the 'bang.' Action is always faster than reaction."