Congress is in the midst of a heated debate over gun control and how best to tamp down on gun violence. And mass shootings like the one that tore through Sandy Hook Elementary School last December are a huge part of that discussion.
So how much do we actually know about mass shootings and the people who commit them? A new study (pdf) commissioned by Mayors Against Illegal Violence* tries to add some much-needed detail.
The researchers pored through the FBI database and recent media reports for every mass shooting since January 2009 — that is, incidents in which at least four people were murdered by guns. Here are their key takeaways, some of them surprising:
MORE: Study: The U.S. has had one mass shooting per month since 2009.