Oklahoma executed Charles Warner on Thursday night, marking the first execution carried out in the state since the botched lethal injection of Clayton Lockett last year.

Warner was declared dead at 7:28pm CST after a procedure that reportedly lasted 18 minutes. While he showed no signs of apparent physical distress, he said out loud, "My body is on fire."

"It hurts," he said. "It feels like acid."

According to Associated Press media witness Sean Murphy, Warner also said he had been struck with the needle five times.

After his microphone was turned off, Warner could still be heard from inside the chamber, where he said, "I'm not afraid to die."

Convicted in 1997 of raping and killing an 11-month-old girl, Warner was scheduled to be put to death on April 29, 2014, the same night as Clayton Lockett. His execution was put on hold when Lockett began groaning and writhing in pain on the gurney after being injected with the lethal cocktail and declared unconscious; concerns over the drugs used in executions prompted state officials to put a temporary hold on death sentences until an investigation had been completed.

Warner's attorneys had asked the U.S. Supreme Court for a stay of execution, arguing that the first of three drugs in the cocktail—midazolam—was not sufficient for sedation. The court denied the stay in a 5-4 decision.

Justices Sonia Sotomayor, Ruth Bader Ginsburg, Stephen G. Breyer, and Elena Kagan voted to stay the execution, but were outnumbered.

"Petitioners have committed horrific crimes, and should be punished," Sotomayor wrote in the dissenting opinion. "But the eighth amendment guarantees that no one should be subjected to an execution that causes searing, unnecessary pain before death. I hope that our failure to act today does not portend our unwillingness to consider these questions."

Madeline Cohen, one of Warner's attorneys, reiterated on Thursday night that the midazolam had not been "approved for general anesthesia."

"[B]ecause Oklahoma injected Mr Warner with a paralytic tonight, acting as a chemical veil, we will never know whether he experienced the intense pain of suffocation and burning that would result from injecting a conscious person with rocuronium bromide and potassium chloride," Cohen said.