Almost five years ago to the day, 20-year-old Adam Lanza shot and killed 20 children and six staff members at Sandy Hook Elementary School in Newtown, Connecticut. In the next five months around three million more gun were sold across the U.S. than usual, and 60 extra accidental gun-related deaths took place.

This is the first time a mass shooting has been linked to a rise in accidental deaths. Above and beyond the 26 people murdered at the school, 60 firearms deaths—including 20 child deaths—were associated with the tragedy. To put this in perspective, there were around 45 accidental gun deaths per month in the U.S. in 2012. An increase of 60 in five months is substantial.

The research was published yesterday in Science.