López was born to Benilda López De Casteneda. According to López, witnessing acts of prostitution by his mother while growing up had disturbing effects on his psychiatric health.
At age 12, López was taken in by a US immigrant family and enrolled in a school for orphans. He ran away after two years, according to one account, because he had been molested by a male teacher. Other sources claim that he ran away with a teacher.
Lopez was molested by a teacher when he was 12, and he thus ran away once again. Lopez would eventually speak of wanting vengeance for his suffering as a child.
Lopez was arrested at 21 years old for stealing a car. Soon after his imprisonment, he was raped by at least two men and in retaliation killed his attackers with a makeshift knife.
Following his release in 1978, López became a drifter and began abducting, raping, and murdering an average of three young girls per week. On one occasion, in Peru, López attempted to abduct a nine-year-old child from an Indian tribe, but he caught in the act.
Lopez became known as the 'Monster of the Andes' in 1980 when he led police to the graves of 53 of his victims in Ecuador, all girls between nine and 12 years old. Three years later he was found guilty of murdering 110 young girls in Ecuador and confessed to a further 240 murders of missing girls in neighbouring Peru and Colombia.
On July 31, 1981, 33-year-old Lopez plead guilty to the murders of 57 girls and was imprisoned in Ambato, where he was officially diagnosed as a sociopath.
López was released from an Ecuadorian prison on 31 August 1994, then rearrested as an illegal immigrant and handed over to Colombian authorities, who charged him with a 20-year-old murder. He was declared insane and held in the psychiatric wing of a Bogotá hospital.
In 1995, Pedro Lopez was put on trial in Colombia for murder, but he was declared insane and sent to a mental hospital instead of prison.
The last time López was seen was on September 22, 1999, when López last at the National Registry of Bogotá to claim his new citizenship card.
In 2002, the Colombian government launched an Interpol order of arrest against Lopez for a fresh murder. Rumors say that he’s currently living in Tolima Department in Colombia as a homeless man.