Forty-seven of these mass shootings have occurred since 2006.Seven of them took place in 2012 alone, including Sandy Hook.
The following analysis covers our original dataset comprised of 62 cases from 1982-2012.
Weapons: Of the 143 guns possessed by the killers, more than three quarters were obtained legally.
A recent analysis of this database by researchers at Harvard University, further corroborated by a recent FBI study, determined that mass shootings have been on the rise.
We've gathered detailed data on more than three decades of cases and mapped them below, including information on the attackers' profiles, the types of weapons they used, and the number of victims they injured and killed.
We exclude shootings stemming from more conventional crimes such as armed robbery or gang violence.
Other news outlets and researchers have published larger tallies that include a wide range of gun crimes in which four or more people have been either wounded or killed.
In Newtown, Connecticut, the attacker wielded a .223 Bushmaster semi-automatic assault rifle as he massacred 20 school children and six adults. (See Goleta, Calif., in 2006.) The average age of the killers was 35, though the youngest among them was a mere 11 years old.
The perpetrators: More than half of the cases involved school or workplace shootings (12 and 20, respectively); the other 30 cases took place in locations including shopping malls, restaurants, and religious and government buildings. (See Jonesboro, Ark., in 1998.) A majority were mentally troubled—and many displayed signs of mental health problems before setting out to kill.
The cases we have documented since then using the revised federal baseline reaffirm our major findings. The horrific massacre at a movie theater in Aurora, Colorado, in July 2012, another at a Sikh temple in Wisconsin that August, another at a manufacturer in Minneapolis that September—and then the unthinkable nightmare at a Connecticut elementary school that December—were some of the latest in an epidemic of such gun violence over the last three-plus decades.