A man who killed a suburban Kansas City gas station attendant in front of the worker's young stepdaughter in 1994 was put to death early Wednesday -- the ninth execution in Missouri this year.

Leon Taylor, 56, was pronounced dead at 12:22 a.m. at the state prison in Bonne Terre, minutes after receiving a lethal injection. With Taylor's death, 2014 ties 1999 for having the most executions in a year in Missouri.

Taylor shot worker Robert Newton to death in front of Newton's 8-year-old stepdaughter during a gas station robbery in Independence, Missouri. Taylor tried to kill the girl, too, but the gun jammed.

Taylor's fate was sealed Tuesday when Gov. Jay Nixon declined to grant clemency and the U.S. Supreme Court turned down his appeal.

Taylor, his body covered by a white sheet, could be seen in the execution chamber talking to family members through the glass in an adjacent room. Once the state started injecting 5 grams of pentobarbital, Taylor's chest heaved for several seconds then stopped. His jaw went slack and he displayed no other movement for the rest of the process.

Four of Taylor's family members sat in a room to his left and looked on without reaction as the drug killed Taylor in about eight minutes. At a time when executions have gone awry in Oklahoma, Ohio and Arizona and taking an extended period to kill an inmate, Taylor's execution went off without any visible hitches or complications with the drug or equipment.

In a written statement, Missouri Attorney General Chris Koster said Taylor "coldly murdered" Newton.

"Those who knew and loved Robert Newton waited two decades for the imposition of justice that finally came early this morning," Koster said.

According to court records, Taylor, his half brother and half sister decided to rob a gas station on April 14, 1994. Newton was at the station with his stepdaughter.

Taylor entered the store, drew a gun and told Newton, 53, to put $400 in a money bag. Newton complied and the half brother, Willie Owens, took the money to the car.

Taylor then ordered Newton and the child to a back room. Newton pleaded for Taylor not to shoot him in front of the little girl, but Taylor shot him in the head. He tried to kill the girl but the gun jammed, so he locked her in the room and the trio drove away.

"She had the gun turned on her," said Michael Hunt, an assistant Jackson County prosecutor who worked on the case. "It didn't fire. If it had fired, we'd have had a double homicide."

Hunt said the child's testimony at trial was pivotal in the death sentence.

"You can imagine what a horrible crime this was, but when you see it coming out of a young person like that, it was hard to listen to," Hunt said.

Taylor was arrested a week after the crime when police responded to a tips hotline call.

Court appeals claimed the death penalty for Taylor was unfair for several reasons.

Taylor's original jury deadlocked and a judge sentenced him to death. When that was thrown out, an all-white jury gave Taylor, who was black, the death sentence.

In 2002, the U.S. Supreme Court ruled that only a jury could impose a death sentence. Taylor's lawyers contended that a Missouri Supreme Court ruling after the U.S. Supreme Court decision led the state to commute at least 10 other death sentences for inmates sentenced by a judge to life in prison -- everyone except Taylor.

Attorney Elizabeth Carlyle said Taylor essentially was penalized for successfully appealing his first conviction.

The clemency request to Nixon said Taylor turned his life around in prison, becoming a devout Christian who helped other prisoners. The petition also cited abuse Taylor suffered as a child, saying his mother began giving him alcohol when he was 5 and that he later became addicted to alcohol and drugs.