Introduction: The term serial killer was coined in the 1970s by a man named Robert Ressler. He chose serial killer as a name to describe a killer who kills three or more victims over a period of time because the FBI always studied a series of cases created by the killers (Freeman, 2007). Serial killers have existed for centuries, since ancient times. Many studies have been conducted to try to understand how the minds of serial killers work, so that the FBI can catch them and find a way to stop them. Not all serial killers are the same, this makes it difficult to understand them and provide a clear definition of how their mind works. Most serial killers have similar character traits and can be classified into different categories to make it easier to find patterns and reasons why they are killing. Early Indicators of Someone Becoming a Serial Killer: In 1963, J.M. MacDonald put together a list of attributes/characteristics that are now considered early indicators of violence; this list was later called MacDonald's Triad. These characteristics include burning, animal cruelty, and enuresis; these traits are often first noticed when they are children. Fire setting often begins with the child's curiosity about what happens when a fire is lit, but then becomes a way for the child to deal with stress and anger. It is an act of “speaking up” because the child feels like no one is listening and wants attention. This trait/behavior may become more dangerous if the child continues to feel the need to relieve stress/anger by lighting fires, because they will start to light larger fires and experiment more with fires. Animal cruelty is another major factor in MacDonald's Triad; is……middle sheet……violent behavior: myth or reality?”. SerialKillerLab. Retrieved March 28, 2014, from http://serialkillerlab.blogspot.ca/2013/04/macdonald-triad-as-predictor-of-violent.htmlCharney-Perez, J. (2005, April 1). “History of serial killers”. Serial killers. Retrieved April 23, 2014, http://iml.jou.ufl.edu/projects/spring05/charney-perez/history.htm“Macdonald Triad.” Sociopathology. Retrieved April 14, 2014, http://sociopathology.org/tag/macdonald-triad/Scott, SL “What Makes Serial Killers Tick?”. Crime Library. Retrieved April 3, 2014, http://www.crimelibrary.com/serial_killers/notorious/tick/victims_1.htmlDee, C. (2007). Serial killer, up close and personal: into the world of torturers, psychopaths and murderers. Berkeley, California: Ulysses Press.Roland, P. (2006). The Crimes of Jack the Ripper. London: Arturo.