A south Texas man who bludgeoned and slashed a 12-year-old boy to death and then revealed to authorities that voices compelled him to drink the victim's blood is set to be executed via lethal injection Wednesday, April 6, at the state's death chamber in Huntsville.

Pablo Vasquez, 38, will be put to death at 6 p.m., which will mark the sixth execution in Texas since the start of 2016, as well its 537th overall - the most of any state - ever since the U.S. Supreme Court reinstated the the death penalty in 1976. That is, however, if it actually goes through.

Vasquez's lawyer, James Keegan, has launched a last-minute appeal to halt the execution, saying in a petition filed with the U.S. Supreme Court that there should be a reprieve so justices can determine whether Vasquez was denied fair punishment because several potential jurors were dismissed if they voiced objections to the death penalty or said they were uncomfortable making such a decision.

This appeal comes after courts as recent as last month rejected arguments that Vasquez had mental health problems and suffered from learning disabilities. As such, the lawyers have also raised questions of ineffective counsel at trial and initial appeal.

The incident this case revolves around dates back to April 18, 1998, when Vasquez, his 15-year-old cousin, Andres Rafael Chapa, and the victim, David Cardenas, were on their way home from a party in Donna, Texas. Vasquez, who admitted to being drunk and high at the time, confessed to police that he heard voices in his head that eventually convinced him to kill Cardenas upon reaching a wooden shed near where his body was found.

The murder had already raised concerns of satanism at the time, since police, who received an anonymous tip about the murder, found Cardenas under a pile of metal sheets with his arms missing, no skin on the back and a hole in his head. Those fears were stoked after Vasquez confessed to the murder and revealed that he also drank his blood.

Beyond the murder, which was committed by hitting the victim in the head with a pipe and cutting his throat, court records indicate that the body was mutilated "by some means that caused bones to shatter."

It took the jury an hour to find Vasquez guilty, and despite concerns about satanism being prominent at the time, the subject never came up during the trial or in the appeals.

In the meantime, Chapa, who was a co-defendent in the case, was charged with murder and is serving a 35-year prison term, while three of their relatives, one of whom was deported to Guatemala, received probation and a small fine for helping to cover up the incident.