There has been another school shooting in the United States. This time it was at Michigan State University in East Lansing. The gunman killed three students and critically injured five before killing himself.

What would be an unthinkable tragedy in any other country is so common in the United States that two MSU students who were physically unharmed in this attack also survived previous school shootings. One student was a sixth grader at Sandy Hook Elementary School in Newtown, Connecticut, in 2012 when a gunman killed 26 students, teachers and staff. Another student was a senior at Oxford High School in Oxford Township, Michigan, in 2021 when a teen gunman killed four of his schoolmates. As is also common in the U.S., before the week was out, there was a second shooting, this one at a shopping center in El Paso, Texas. It left one person dead and three injured.

Criminologists David Riedman and James Densley, who maintain databases of mass shootings in the U.S., explain how the MSU attack compared with previous ones, shedding light on how future tragedies could be averted.

Their research shows that mass shooters tend to be boys and men who are in a noticeable crisis and communicate their intent to do harm before they pull the trigger. What’s more, if family, friends and co-workers know the warning signs of violence and how to report them, there is an opportunity to stop violence from occurring.