The mass shootings where stricter gun laws might have made a difference

If the key gun control proposals now being considered in Congress had been law since 1999, four gunmen younger than 21 would have been blocked from legally buying the rifles they used in mass shootings.

At least four other assailants would have been subject to a required background check, instead of slipping through a loophole. Ten might have been unable to steal their weapons because of efforts to require or encourage safer gun storage. And 20 might not have been allowed to legally purchase the large-capacity magazines that they used to upgrade their guns, helping them kill, on average, 16 people each.

Taken together, those four measures might have changed the course of at least 35 mass shootings — a third of such episodes in the United States since the massacre at Columbine High School in Colorado, a New York Times analysis has found. Those 35 shootings killed a combined 446 people.