DENVER -- Seventeen years after a shooting spree at a Chuck E Cheese restaurant, the gunman is one step closer to execution.

Tuesday, the U.S. District Court upheld Nathan Dunlap’s death sentence.

Dunlap had recently been fired from the restaurant in Aurora in December 1993. Prosecutors said he walked into the restaurant around 9 p.m., sat at a table alone, ordered a sandwich, called his girlfriend, played a video game and spoke with an employee.

Prosecutors said around 9:50 p.m., Dunlap went to the men’s bathroom and waited for the restaurant to close.

At approximately 10:10 p.m. Dunlap walked back into the restaurant, approached Sylvia Crowell, 19, at the salad bar and shot her, prosecutors said.

Prosecutors said Dunlap then shot Ben Grant, 17, who was vacuuming, then shot Colleen O’Conner, 17.

Dunlap reportedly then went to the kitchen and shot Bobby Stephens, 19.

Prosecutors said Dunlap went into the back office and demanded manager Marge Kohlberg, 52, open the store’s safe. After she complied, prosecutors said, Dunlap shot her twice.

Dunlap took about $1,500 from the safe along with Chuck E. Cheese keychains and arcade game tokens and left, prosecutors said.

One shooting victim, Stephens, managed to run out an emergency exit, get to a nearby apartment complex and call for help.

Stephens survived, but four people died.

Dunlap was questioned by police the night of the murders and was arrested the next day. He was charged with four counts of deliberative murder, four counts of felony murder, attempted first-degree murder, attempted first-degree felony murder, first-degree burglary, first-degree assault, aggravated robbery, theft and three violent crimes.

Prosecutors said Dunlap appealed his sentence, but he did not appeal his conviction. The Colorado Supreme Court found that Dunlap’s Chuck E. Cheese murders were "cold-blooded executions" committed "with a brutal contempt for human life." The Colorado Supreme Court also denied appeals in 2001 and 2007.

In Tuesday's ruling from the U.S. District, Senior U.S. District Judge John L. Kane wrote, "In the final analysis, Dunlap was competently represented, fairly tried, and duly sentenced to death for having committed four vicious murders of three teenagers and a mother of two children for no intelligible reason at all."

It goes on to say, "the processes of the law have been exhausted, the defendant’s guilt is uncontestable and the penalty, awesome and stark as it is, meets every requirement of the law."

Family members of the victims told 7NEWS in 2007 that they didn't understand why it was taking so long to carry out the sentence against Dunlap.

"Don't get me wrong, I am not a violent type guy. I just think the public deserves justice, " said Bob Cowell, Sylvia Cowell's father.

If Dunlap and his attorney decide to continue his appeals, the next step is to appeal to the 10th Circuit Court of Appeals.

Read the entire U.S. District Court Ruling on Nathan Dunlap.