How common are mass shootings in the U.S.?

Posted at 3:44 PM, Dec 02, 2015
and last updated 2015-12-03 12:03:54-05

A week after a lone gunman took the life of three people in Colorado Springs, tragedy has struck Southern California as multiple people have been killed at a disability facility in San Bernardino. 

Here is some insight on how often these crimes happen: