A suspected serial killer convicted of killing a 13-year-old girl and attempting to kill another girl is scheduled to be executed on Thursday in Texas, a day after an appeals court rejected his challenge regarding the drugs to be used in his lethal injection.

The state, which executes more people than any other in the United States, is set to execute Tommy Lynn Sells, 49, at 6 p.m. at a prison in Huntsville.

On Wednesday, the U.S. Court of Appeals for the Fifth Circuit overturned a temporary stay of execution for Sells. A federal judge hours earlier had granted that stay, finding that Texas had hidden information about the supplier of the drugs.

The appeals court said the case might be different if the state were using a drug never before used or unheard of, whose effectiveness was completely unknown, which was not the case.

Other appeals on Sells’ behalf are pending on Thursday with the U.S. Supreme Court.

Sells was convicted of stabbing a 13-year-old girl to death and attempting to kill a 10-year-old girl on New Year’s Eve of 1999 at the Del Rio home of a man who owed him drug money, according to court documents.

After an evening of drinking beer, Sells went to the house to sexually assault the girl as payback for the drug debt. He broke in, found her sleeping on a bunk bed and began to assault her. When she awoke, he stabbed her multiple times and slashed her throat, killing her, court documents showed.

Sells then slit the throat of a 10-year-old girl, who was sleeping in the top bunk. After he fled, that girl walked to a nearby neighbor’s house to get help, according to court documents.

According to various media reports, Sells confessed to as many as 70 murders, starting when he was 16 years old.

Sells would be the 15th person executed in the United States this year and the fifth in Texas if the execution is carried out, according to the Death Penalty Information Center, which monitors executions.

Texas has executed 512 people since the U.S. Supreme Court reinstated the death penalty in 1976.