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It is not a secret that some serial killers have good mental health, so, the relation between a desire to kill and mental diseases is controversial. Some serial killers think that they kill bad people thus they believe that they are doing the right thing.
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Moreover, personal experiences can make people hate the whole world and kill other people.
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This kind of attitude is related to different social, political, or even economic factors. So, a serial killer kills other people not only because of his/her mental health. Many people in the world suffer mental diseases, but not all of them are serial killers. The thing that distinguishes serial killers from other killers is that they intentionally and continuously kill other people mostly for psychological reasons.
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A serial killer is a person who has killed more than two people in two or more separate events on purpose.
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