[3][4] Early in the morning of September 2, 1990, Prieto, along with 29-year-old Vincent Lopez and 33-year-old Danny Sorian, robbed Anthony Rangela in Ontario.

Twelve days later, he was transferred to San Quentin State Prison, where he would spend the next 14 years awaiting execution on death row.

On June 2, 1990, Prieto killed Lula Mae Farley in an alley behind an Ontario supermarket where she and her husband were collecting recyclables, according to 1990 news coverage.

Following these revelations, the Fairfax County Attorney's Office brought a number of charges against Alfredo Prieto, resulting in his extradition from San Quentin on April 28, 2006, to Virginia, where he was due to stand trial.

However, the trial judge was forced to declare a mistrial during the penalty phase, after one juror claimed he had been peer pressured into going along with the guilty verdict.

[14] Prieto's lawyers filed an appeal, and the Virginia Supreme Court overturned the sentence based on an error in the jury verdict form.

[15] A year later, his lawyers filed another appeal to overturn his sentence and asking for a new trial, based on the results from a psychiatric exam which determined that their client was intellectually disabled, with an IQ threshold between 67 and 73.

Their petition was accepted, but at the third trial, the prosecutor's office proved to the court that Prieto had been a successful student at school in both El Salvador and the United States, and that he had adapted socially, had perfectly learned the English language, was popular and obtained a driver's license in both Virginia and California, which contradicted the notions of an intellectual disability.

[15][16] On October 1, 2015, Prieto was executed by lethal injection at the Greensville Correctional Center at 9:17 p.m., in the presence of state witnesses and some of the victims' family members.

They demanded information about the shelf life of pentobarbital, which the state had received from Texas in exchange for another sedative, midazolam, which had expired.

Among other things, his lawyers sought to force the state to disclose the name of the pharmaceutical company producing the drug in order to determine its quality so they could prevent the physical torture of their client during the execution, but this suit was dismissed.