A recent report out by the Advanced Law Enforcement Rapid Response Training center looked at more than a hundred active shooter events, which are defined as one or more persons whose primary motive is mass murder in a confined or populated area, not including gang and family-related shootings. The researchers found the number of these types of mass shootings has increased, from an average of about 5 a year prior to 2009, to 15 in 2013.

Events that led to the latest school shooting in New Mexico are not uncommon.