What explains U.S. mass shootings? International comparisons suggest an answer

Franklin Zimring and Gordon Hawkins study cited by The New York Times, Nov. 7, 2017

The United States is not actually more prone to crime than other developed countries, according to a landmark 1999 study by Franklin E. Zimring and Gordon Hawkins. … American crime is simply more lethal. … They concluded that the discrepancy, like so many other anomalies of American violence, came down to guns.