Special investigator and psychologist Jill Peterson and sociologist James Densley built The Violence Project, the first comprehensive database of mass shooters. Their goal was to establish the root causes of mass shootings and figure out how to stop them by examining hundreds of data points in the life histories of more than 170 mass shooters-from their childhood and adolescence to their mental health and motives. They've also interviewed the living perpetrators of mass shootings and people who knew them, shooting survivors, victims' families, first responders, and leading experts to gain a comprehensive first-hand understanding of the real stories behind them, rather than the sensationalized media narratives that too often prevail. For the first time, instead of offering thoughts and prayers for the victims of these crimes, Peterson and Densley share their data-driven solutions for exactly what we must do, at the individual level, in our communities, and as a country, to put an end to these tragedies that have defined our modern era.