STARKE, Fla. -

A Florida man convicted of killing a police officer during a traffic stop 33 years ago has been executed at the Florida State Prison.

Manuel Valle, 61, was administered a lethal injection and pronounced dead at 7:14 p.m. Wednesday, the governor's office reported. Valle was the first Florida inmate to face execution using the state's newly revised mix of lethal drugs, a concoction that faced legal challenges which twice delayed carrying out the death sentence.

Valle fatally shot Coral Gables officer Louis Pena on April 2, 1978, after Pena stopped Valle for a traffic violation while driving a stolen car, according to court records. He also shot fellow officer Gary Spell, who survived and would testify against Valle in court.

More Information: State of Florida Death Row Website

Spell testified that when he arrived the day of the shooting, Valle was seated in Pena's patrol car. As Pena was checking the license plate of the car Valle had been driving, Valle walked back to the car, reached inside and then walked back and fired a single shot at Pena, the records indicate. He then fired two shots at Spell, who was saved by his bulletproof vest, the records show. Valle fled and was arrested two days later.

A 4 p.m. EDT execution was scheduled, but the office of Gov. Rick Scott said when that time elapsed that the execution was being delayed because of an 11th-hour attempt to stop it before the U.S. Supreme Court. The high court announced Wednesday evening it had declined to intervening, allowing the execution to go forward.

Southern prisons had seen a spate of executions in recent days.

On Sept. 21, Georgia executed Troy Davis for the 1989 shooting death of a policeman, despite an international outcry and claims he was innocent. The same day, Texas executed white supremacist Lawrence Russell Brewer for the 1998 hate crime and dragging death of James Byrd Jr., a black man. A day later, Alabama executed Derrick O. Mason for the shooting death of a store clerk during a 1994 robbery.

Pena's son, also named Louis Pena, stood outside the Florida prison Wednesday afternoon as he awaited word whether the execution would go forward as scheduled. He said that step would mean closure for his father.

"It means finally, my dad's soul is put to rest after 33 years," said Pena, who was 19 when his father died and is now 53 years old.

"He killed a cop in cold blood ... He killed a cop and lived 33 years. This man lived another lifetime after taking a life," Pena added.

Valle was initially sentenced to die in 1981, but the state Supreme Court ordered a new trial that year. He was again convicted and sentenced to die, but the U.S. Supreme Court vacated that death sentence in 1986. Another jury recommended the death sentence anew in 1988.

Since Scott signed Valle's death warrant, the original Aug. 2 execution date has been delayed twice -- once by the Florida Supreme Court and then by the 11th U.S. Circuit Court of Appeals in Atlanta. Both courts later rejected arguments by Valle's lawyers that the new drug mix would cause him pain, and therefore be cruel and unusual punishment.

The state previously used sodium thiopental to render condemned prisoners unconscious before the second and third drugs, pancuronium bromide and potassium chloride, were injected. But sodium thiopental is no longer manufactured in the United States and now Florida and other states are substituting it with pentobarbital, which is marketed under the name Nembutal.

Eighteen people have been executed around the country using pentobarbital as a replacement anesthetic since Oklahoma became the first last year.

Valle's warrant was the first Scott has signed as governor. It comes in a year when there have been an unusually high number of police officers killed in Florida. Six officers have been fatally shot in 2011, according to the Officer Down Memorial Page, a website that tracks officer deaths nationally. That's already more than each of the last three years and one shy of the seven officers killed by gunfire in 2007.

Valle was calm earlier Wednesday and had met with several relatives before the execution, Department of Corrections spokeswoman Gretl Plessinger said.