Serial Killers Fast Facts Here’s a select list of convicted American serial killers and notable open or unsolved cases. Serial murder is defined by the FBI as two or more killings separated by a span of time. A majority of serial killings are sexually motivated, according to the FBI. Serial murders are relatively rare. Fewer than one percent of homicides during a given year are committed by serial killers, the FBI reports. David Berkowitz Years and location: 1970s, New York City Characteristics: Initially claimed a neighbor’s dog was possessed by an ancient spirit that commanded him to shoot people. The dog owner’s name was Sam. Berkowitz later said the dog story was a hoax.