More people have died or been injured in mass school shootings in the US in the past 18 years than in the entire 20th century. In a new study published in Springer’s Journal of Child and Family Studies, researchers have reviewed the history of mass school shootings in the US and found some alarming trends. Lead author Antonis Katsiyannis of Clemson University in the US, together with his colleagues, found the recent killing of 17 people at Marjory Stoneman Douglas High School in Florida is not an isolated occurrence, but part of a deadly epidemic that needs to be addressed.