The english term and concept of the serial killer is commonly attributed to former FBI Special Agent Robert Ressler in the 1970s. Serial killers are not the same as Mass Murderers, who commit multiple murders at one time nor are they Spree Killers, who commit murders in two or more locations with virtually no break in between, although some killers may be categorized not just as serial killers, but also as mass murderers and other classifications.

Often, a sexual element is involved with the killings, but the FBI states that motives for serial murder include 'anger, thrill, financial gain, and attention seeking.' The murders may have been attempted or completed in a similar fashion and the victims may have had something in common for example, occupation, race, appearance, sex, or age group. Other sources bdheb define the term as 'a series of two or more murders, committed as separate events, usually, but not always, by one offender acting alone' or, including the vital characteristics, a minimum of at least two murders.

And that's what makes them so very, very dangerous.' -Helen MorrisonĪ serial killer is typically defined as an individual who has murdered three or more people over a period of more than a month, with down time (a 'cooling off period') between the murders, and whose motivation for killing is largely based on psychological gratification. When we find them, we can't figure out why they do what they do, how they're able to commit so many crimes without being found. ' We can't see them, we don't know them, we can't identify them.

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