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

Posted: 12:03 PM, Dec 03, 2015
Updated: 2015-12-03 17:03:55Z

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: