JACKSONVILLE, Fla. -- The U.S. Supreme Court on Thursday halted the execution of convicted child killer Mark Schwab.

The move by the high court -- widely expected as it considers the appeals of two Kentucky inmates challenging the same lethal toxic three-drug combination used in Florida -- came hours after the 11th Circuit Court of Appeals in Atlanta ruled the execution could proceed.

It was planned for 6 p.m. Thursday.

The stay of execution comes as the high court has agreed to hear the appeals of two Kentucky inmates challenging the drugs used for lethal injection.

Florida uses the same drugs and Schwab's attorneys claim the chemicals violate the Eighth Amendment ban on cruel and unusual punishment.

Schwab was convicted of raping and murdering 11-year-old Junny Rios-Martinez 16 years ago in Brevard County.

Schwab had been released from prison after serving three years of an eight-year sexual assault sentence when he kidnapped, raped and strangled Junny. Schwab left the boy's body in a footlocker in a rural part of Brevard County.

The Florida Legislature later passed the Junny Rios-Martinez Act, which prohibits sex offenders from early release from prison.

"My heart goes out to the family of Junny Rios as they wait for justice to be served in this particularly distressing case," Florida Attorney General Bill McCollum said in a statement. "I respect the Court's authority to grant this stay, but the Attorney General's Office will continue to be engaged in this process and will make every argument possible to move this case toward the appropriate resolution."

The decision 11th Circuit Court of Appeals in Atlanta comes one day after a federal court in Orlando blocked the execution. It noted that the Supreme Court has not yet ruled in the Kentucky case, allowing Schwab's execution to go forward.