In 2015, 367 people were killed and 1,317 people were injured in mass shootings, according to a crowd-sourced database at www.shootingtracker.com. In the video above, we have plotted every death and injury from a mass shooting over the course of the year -- a total of 374. You can also see newspaper headlines and 911 calls for some of the shootings.
The database uses a definition of mass shooting as four or more people shot or killed, including the shooter. There is no federal definition of a "mass shooting." The FBI used to consider someone a "mass murderer" if they killed four or more people during one event, regardless of weapons used. But starting in 2013, federal statutes defined "mass killing" as three or more people killed. And unlike the tracker, the tally doesn't include the killer if he or she is eventually killed by law enforcement or takes his or her own life.
Some argue the "mass shooting" definition employed database is too broad since it can include everyday violence -- such as within the home or gang activity -- while others argue the database vividly portrays the daily toll of incidents in America where firearms are used to injure or kill multiple Americans at the same time. As the nation has endured several years of prominent shootings, including in San Bernardino, Calif., on Wednesday, the database has become a source of data for stories for national media.
You can also determine the number of annual mass shootings by different metrics with our tool.