Serial killers are responsible for less than one percent of all murders in the United States, yet their crimes have an outsized impact due to their brutality, repetition, and psychological complexity. The FBI defines a serial killer as someone who murders two or more victims in separate events, typically with a cooling-off period between killings. Most offenders are male, often white, and operate between the ages of 25 and 45, though notable exceptions exist. Common motives include power, control, sexual compulsion, or a distorted sense of mission. Many display organized behavior—planning abductions, concealing evidence, and following strict rituals—while others act in disorganized, impulsive ways linked to mental illness or delusion. Serial killers often follow patterns known as a modus operandi (method of operation) and a signature (psychological ritual unique to the offender). Famous examples like Ted Bundy, Jeffrey Dahmer, and Gary Ridgway highlight how forensic science, behavioral profiling, and victimology have evolved to track these offenders and prevent future killings.