The study of those who murder more than once is replete with assumptions and speculations about causality. Two views frequently encountered are that the multiple murderer’s behavior is a mystery or that every multiple murderer is suffering from some type of psychiatric disorder. A common assumption found in the media and in the professional literature is that these murderers are “crazy”. Actually, after identification, most multiple murderers have been described as withdrawn, shy, and generally nondescript (…).
☛ BUSCH, Katie A. & CAVANAUGH, Jr., Jame (1986). “The Study of Multiple Murder. Preliminary Examination of the Interface Between Epistemology and Methodology”, Journal of Interpersonal Violence, Vol. 1, No. 1, pp. 5-23. Online / PDF
Regarding the recent Cumbria shootings (involving taxi driver Derrick Bird).