10 of the World's Most Prolific Serial Killers

Pedro Alonso Lopez
Two women mourn for their beloved during the funeral for people killed in a bus accident in Quito, Ecuador, in 2006. In 2002, Pedro Alonso Lopez received 14 years in prison in Ecuador for killing hundreds of people, mostly young girls. RODRIGO BUENDIA/AFP/Getty Images

The "Monster of the Andes" is considered to be the world's most prolific serial killer. Lopez was the son of a Colombian prostitute who tossed him out in the streets, where he reportedly suffered sexual assaults from a man who took him in. Lopez vowed to do to girls what had been done to him. In the 1970s, he turned into an international predator, roaming across Colombia, Ecuador and Peru in search of vulnerable pre-pubescent girls [source: Biography.com, Wilson and Seaman]. In 1980, after a river overflowed its banks near the mountain town of Ambato in central Ecuador, four makeshift graves were uncovered, and the bodies of some of Lopez's victims floated free. Not long afterward, Lopez was cornered by a street vendor and her neighbors as he tried to abduct yet another potential victim, the vendor's 11-year-old daughter [source: Biography.com, Wilson and Seaman].

Lopez confessed his crimes to an undercover detective and led police to the graves of 59 of his victims. But the actual death toll was much higher — estimated at 350 to 360. A very sick man, Lopez said he only killed the girls in the daylight: "It was only good if I could see her eyes." [source: Associated Press, Laytner].

Even so, Lopez only served 14 years for his crimes in Ecuador, and another four years in a Colombian mental institution. After being released in 2002, he vanished, and his whereabouts are unknown [source: Biography.com].

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