The death tolls change, the places change: Nine in a church, 23 in a restaurant, 26 in an elementary school, 14 at a holiday party. The faces in the memorial photos change the most. But the weapons are the common denominator. Mass killings in the United States are most often carried out with guns, usually handguns, most of them obtained legally. There is no universally accepted definition of a mass shooting, and different organizations use different criteria. In this... (GunPolicy.org)