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Chuck E. Cheese's Killer Faces Execution
PHOTO: This undated photo provided by the Colorado Department of Corrections shows Nathan Dunlap.

The Supreme Court has refused an appeal from so-called Chuck E. Cheese's murderer Nathan Dunlap, opening the door for a Colorado judge to schedule the state's first execution in over 15 years.

The killing of four employes in a Chuck E. Cheese's in 1993 was a massacre that scarred the people of Aurora, Colo., long before shooter James Holmes opened fire in a crowded movie theater on July 20, 2012. Holmes killed 12 and wounded dozens more.

Dunlap, 38, is one of three men on the state's death row. He was sentenced to death in 1996, but the victims' families have been waiting for justice to be carried out for nearly 20 years.

"I don't know if Dunlap is ever going to be executed," Sylvia Crowell, the mother of a victim, told ABCNews.com today. "Whether he dies from natural causes or from execution doesn't matter to me, but he better not leave that prison except in a pine box."

Click here for more on Aurora's other massacre.

The case will now go back to the trial court, which is the Arapahoe District Court, according to Carolyn Tyler, spokeswoman for the state Attorney General's office. The Arapahoe court would set a date for execution.

Though Dunlap's guaranteed appeals have run out, his attorney could potentially still file a stay, which would give them the opportunity to present a clemency application to Gov. John Hickenlooper. All of the potential steps leave the timeline for a potential execution unclear.

Crowell's 19-year-old daughter Sylvia was killed during the Dec. 14, 1993 shooting. Sylvia was closing the salad bar at closing time when Dunlap, who was also 19 at the time, came up behind her and shot her in the head. He had recently been fired from the restaurant.

He went on to kill Ben Grant, 17, as he cleaned nearby and Colleen O'Connor, 17, who was cleaning the rowdy restaurant's quiet room for adults when Dunlap approached her. She begged for her life, but he showed no mercy. Dunlap also killed the restaurant's 50-year-old manager Margaret Kohlberg.

He also shot Bobby Stephens in the jaw and Stephens, 20 at the time, was the sole survivor.

Dunlap was sentenced to the die, but has been sitting on death row for nearly 20 years as he has moved through the judicial system's lengthy appeals process. The Crowells attended Dunlap's trial and nearly every appeal hearing.

There are currently three inmates on death row in Colorado, which has executed only one prisoner, in 1997, since the death penalty was reinstated in 1984.

"We've been frustrated by this for so long," Crowell, 71, said. "When this whole thing bubbled up, we were told, 'Don't get your hopes up.'"

"I have no idea if any of us will be invited to the execution. I don't know the etiquette," she said. "I have no intentions of going myself. Our son Daryl would like to attend, but I don't regard that as a particularly wise decision."

"We think it would be a grave miscarriage of justice if he left the prison, except dead," she said.

Dunlap's attorney believes that he should spend the rest of his life in prison.

"I can't really discuss what we're going to do next," Dunlap's attorney Phil Cherner told ABCNews.com. "Mr. Dunlap should spend the rest of his life in prison without the possibility of parole."

"However, given what we know about the unfair and disproportionate use of capital punishment in Colorado, it really would be unconscionable for the state to carry out his death sentence," he said.

Crowell said that Coloradans refer to the state's tragedies as "the three c's" -- Columbine, Chuck E. Cheese's and the Century 16 movie theater. The Crowells live off a main road less than two miles from the movie theater.

"Every time we hear a siren, we think, 'There goes someone else's day ruined."

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