Zusha Elision:

The 14-year-old charged with killing two students and two teachers at a Georgia high school this week cut a sickeningly familiar figure: A troubled teen who had been reported to authorities for alleged past threats to carry out a school shooting.

Most mass shooters let the world know they are going to strike. When researchers at the Secret Service’s National Threat Assessment Center studied school attacks between 2008 and 2017, they found that 77% of perpetrators threatened their targets or shared their intentions beforehand.

So why can’t they be stopped?

In the growing field of threat assessment, professionals say there is a way to stop them long before they pick up a gun. These experts work at schools, businesses and police agencies to identify, evaluate and manage threats with interventions such as monitoring, therapy or, in extreme cases, arrest.