Once again, definitions are relevant to the study of terrorism's relationship to mass shootings. What qualifies as a terrorist act?
There is no single definition of terrorism, either within the U.S. or internationally. The rise of "lone wolf" terrorists, who may "self-radicalize" and have no clear ties to known terrorist organizations, further complicates attempts to define terrorist incidents.
Examples of definitions:
For more sources on lone wolf terrorism, see this brief bibliography (PDF).
The San Bernardino incident of Dec. 2, 2015, was investigated by the FBI as a terrorist incident due to " indications of radicalization by the killers and of a potential inspiration by foreign terrorist organizations."
The shooter in Orlando "Pulse" incident of June 12, 2016, claimed allegiance to ISIS, according to FBI reports.
Within the U.S., whether certain other mass shooting incidents should be considered "terrorist" has been a subject of public debate. These include:
Although bombs are perhaps more familiar as weapons of terrorism, notable terrorism-related mass shootings have taken place outside the U.S. in recent history. Selected examples: