How many mass shootings happen each year depends on who you ask and what database you're looking at, according to Tristian Bridges, an associate professor of sociology at the University of California Santa Barbara who studies mass shootings.
Bridges said most media outlets and research organizations define a mass shooting by the number of people killed, which he believes is too conservative and understates the gravity of the problem. Bridges speaks about his research, where he defines a mass shooting as involving three or more people injured by one or two shooters, and how that changes the statistics and why he believes it's a more accurate reflection of the problem.
Bridges' has personal connections to a mass shooting. His graduation from East High School in 1999 coincided with the shootings at Columbine High School and he knew a student who attended the school. And, while he has not experienced a mass shooting himself, East was recently the site of a shooting by a student that wounded two administrators. Earlier this year, an East student was fatally shot while in his car outside of the school.
Bridges said to get an accurate handle on the problem of mass shootings in America, people have to understand how common they are. He also talks about why he believes America needs to rethink its relationship with guns and what role they play in our society and culture.