He was born in El Paso, in the state of Texas on February 29, 1960. He was the youngest son of Mercedes Muñoz and Julián Ramírez, both Mexican immigrants.

With the influence of his cousin still a child, his career as a criminal started early. He used to drug himself with Mike and as is common in addicts, they went out to steal to maintain his vice. With this history it was logical that he ended up locked up soon.

In 1980, in the town of Ambato, in Ecuador, the inhabitants suffered desperate for the sudden disappearance of several young girls from the area. As if it were a highly contagious disease, multiple girls were lost, so it was suspected that perhaps a maniac was stalking the place. The families took precautions and all were awaiting any information that could clarify the matter.

 
Pedro moved to Ecuador. Then he would affirm that, during his stay in that country, he murdered at least three girls a week. He confessed to killing three hundred girls, a fact that the police stopped doubting when Lopez happily led them to the places where he had buried the bodies. The officers affirmed that the assassin did not seem to be ashamed of a bit, but on the contrary showed a kind of pride. He even tried to have a photo taken with the skull of one of his victims.

He was the seventh child of a total of thirteen brothers, children of a prostitute of small stature, and had an unhappy childhood by violence, by the excessive control of his mother and the absence of the father figure.