Just over a month ago a cardiothoracic surgeon was shot and killed at Brigham and Women's Hospital in Boston. JAMA (February 26, 2015) has a "Viewpoint" article entitled "Hospital-Based Active Shooter Incidents: Sanctuary under Fire."
The article can be seen
here.
I don't understand something here. Why is the term "active shooter" being used? What other kind of shooter can there be?