AUSTIN, Texas (Reuters) - A south Texas man who bludgeoned and slashed to death a 12-year-old boy, mutilated the corpse and then drank the blood of his victim was executed on Wednesday at the state’s death chamber in Huntsville, a prisons official said.

Pablo Vasquez, 38, is seen in an undated picture released by the Texas Department of Criminal Justice. Vasquez, a south Texas man who bludgeoned and slashed to death a 12-year-old boy, mutilated the corpse and said he drank the blood of his victim is set to be executed on April 6, 2016 at the state's death chamber in Huntsville. REUTERS/Texas Department of Criminal Justice/Handout via Reuters

Pablo Vasquez, 38, was put to death by lethal injection and pronounced dead at 6:35 p.m., the official said. The execution was the sixth in Texas this year and the 537th since the U.S. Supreme Court reinstated the death penalty in 1976, the most of any state.

About four hours before the planned execution, the U.S. Supreme Court denied a petition to halt the proceedings.

Lawyers for Vasquez has launched the last-minute appeal, saying their client had been denied a fair punishment because prospective, qualified jurors in his trial had been dismissed if they had sympathies against the death penalty.

The lawyers had previously said Vasquez had mental health problems and suffered from learning disabilities.

The victim, David Cardenas, was found under metal sheets in the Texas border town of Donna in 1998. The arms were missing from the corpse, which had no skin on the back and a hole in the back of the head, court papers filed by Texas said.

The incident raised worries at the time about occult rituals, which were stoked when prosecutors produced a taped confession in which Vasquez, then 21, admitted to killing the boy and drinking his blood because voices from the devil told him to do so.

Cardenas, trying to fit in with a group of teenagers and Vasquez, was hanging out with the group near a mobile home, when he was attacked.

Police later received tips of a murder and found the decaying and mutilated body of the 12-year-old, the court papers showed.

Prosecutors said Vasquez hit the victim on the head with a pipe and cut his throat. They also said he stole some jewelry from the victim.

“The body was also mutilated after death by some means that caused bones to shatter,” the court papers said.

It took the jury about an hour to find Vasquez guilty.

A co-defendant, then 15, was sentenced to 35 years in prison on a murder conviction.