His was the first execution in Oklahoma since a controversial lethal injection, which was widely seen as botched
, in April.
Warner was convicted in 2003 for the first-degree rape and murder of his then-girlfriend's 11-month-old daughter in the summer of 1997.
He was executed at the Oklahoma State Penitentiary in McAlester, about 130 miles east of Oklahoma City. Warner was pronounced dead at 7:28 p.m. CT (8:28 p.m. ET).
"Justice was served tonight as the state executed Charles Warner for the heinous crime of raping and murdering an infant," said Oklahoma Gov. Mary Fallin.
A reporter from the Associated Press, Sean Murphy, was among the witnesses. He recounted Warner's last words.
"They poked me five times. It hurt. It feels like acid," Warner said, according to Murphy.
"I'm sorry for all the pain that was caused. I'm not a monster. I didn't do everything they said I did. I love people. I love my family. I love Jesus," Warner said.
He thanked his mother and sister for their support, and said to "tell my baby girl she means the world to me."
According to Murphy, the execution began at 7:10 p.m. CT (8:10 p.m. ET). Once it started, Warner said: "My body is on fire."
"No one should go through this. I'm not afraid to die. We's all going to die," he said.
Other than his statements, Warner did not appear to be suffering and did not show any obvious signs of distress, Murphy told other reporters.
Before the execution, a spokesman with the Oklahoma Department of Corrections had said that Warner was scheduled to be executed using a three-drug combination of midazolam, vecuronium bromide and potassium chloride.
Midazolam, a benzodiazepine that is still not FDA approved, is supposed to render the prisoner unconscious. Vecuronium bromide is a paralytic, which is meant to paralyze all muscle movement and stop respiration. Potassium chloride's role is to activate nerves and induce cardiac arrest.
Warner's attorney, Dale Baich, had filed a motion with the U.S. Supreme Court asking for a stay and asked the court to review Oklahoma's lethal injection policies in general. The court denied the requests.
"Of particular concern is the use of midazolam, which has been involved in several extremely problematic executions, including the gruesome and horrific execution of Clayton Lockett in Oklahoma and the two-hour prolonged death of Joseph Wood in Arizona in July 2014," Baich said.
Warner was originally scheduled for execution on the same night as Lockett -- April 29, 2014 -- but the execution was called off
after the state took 43 minutes to execute Lockett
, a controversial event that was witnessed by media and state officials. Witnesses said Lockett was convulsing and writhing on the gurney, as well as struggling to speak, before officials blocked their view.
The execution was halted, but Lockett eventually died
A team of medical examiners later ruled that Lockett died from the state's lethal injection. The report, which was released in September by the Oklahoma Department of Corrections, called the manner of death a "judicially ordered execution."
Lockett's execution was the first time Oklahoma had used midazolam as the first element in its three-drug cocktail.