Between a 2011 shooting at an IHOP restaurant in Carson City, Nev., that left four people dead and the 2013 attack on the Washington Navy Yard where 12 people were killed, a mass shooting occurred somewhere in America once every 64 days, on average.
In the preceding 29 years, such shootings occurred on average every 200 days, according to an analysis by researchers from Harvard University's School of Public Health and Northeastern University.
The study defined a mass shooting as an outbreak of firearms violence in which four or more victims were killed and the shooter was unknown to most of his victims, the Los Angeles Times reports.
