For all those questions of "What would make a person do something like that?" asked about school or workplace shootings; all the "But he seemed such a nice, quiet young man," spoken of family killers, or serial murderers--here is an answer. Former FBI profiler Joe Navarro categorizes those he refers to "dangerous personalities" into four distinctions:
That last category includes those popularly known as psychopaths and sociopaths. The umbrella of "Predator" is key to identity individuals whose behavior, in aggregate, may range from simply taking advantage, to conning, on to damage, injury, and ultimately, murder.
Mr. Navarro aims at educating a lay audience, and provides clear and recognizable information, minus psychiatric jargon.