What makes serial killers tick? What are their motives? We've listed nine facts about serial killers, according to FBI.gov:

1. "There is no generic profile of a serial killer. Serial killers differ in many ways, including their motivations for killing and their behavior at the crime scene."

2. "Serial killers are not limited to any specific demographic group, such as their sex, age, race, or religion."

3. "Most serial killers are not reclusive, social misfits who live alone. They might not appear strange. Many serial killers hide in plain sight within their communities. Serial murderers often have families and homes, are gainfully employed, and appear to be normal members of the community."

4. "All serial murders are not sexually-based. There are many other motivations for serial murders including anger, thrill, financial gain, and attention seeking."

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5. "Regardless of the motive, serial murderers commit their crimes because they want to. The exception to this would be those few killers suffering from a severe mental illness."

6. "Very few serial murderers travel interstate to kill. Most serial killers have very defined geographic areas of operation. However, serial murderers will, at times, spiral their activities outside of their comfort zone, when their confidence has grown through experience or to avoid detection."

7. "It has been widely believed that once serial killers start killing, they cannot stop. There are, however, some serial killers who stop murdering altogether before being caught."

8. "As a group, serial killers suffer from a variety of personality disorders, including psychopathy, anti-social personality, and others. Most, however, are not adjudicated as insane under the law."

9. "It is not that serial killers want to get caught; they feel that they can't get caught. As serial killers continue to offend without being captured, they can become empowered, feeling they will never be identified. As the series continues, the killers may begin to take shortcuts when committing their crimes. This often causes the killers to take more chances, leading to identification by law enforcement."