DENVER -- A man shot dead inside a Denver sushi bar was attempting to collect a gambling debt from the restaurant owner, 7NEWS has learned.

That owner, Yan De Yang, 40 has been charged with first-degree murder in the Oct. 22 shooting death of Lloyd Running Bear, 29.

Running Bear was shot multiple times in the chest as horrified lunch patrons at Chopsticks and Sushi Restaurant watched. Yang, who remains in jail, was also charged with first-degree assault.

Yang, who uses the first name David, told police he shot in self-defense when Running Bear began choking him, according to police reports. Yang said he had been getting death threats after he threw Running Bear out of his restaurant a week earlier for being drunk.

But Mahesh Hingorani, who was with Running Bear during the shooting, told police "they went to the restaurant to collect [on] a bet from the owner, David," according to court records. Hingorani, who escaped the shooting unharmed, said he was collecting the gambling debt for Hingorani's father.

This supports an account by a restaurant worker who said she overheard Yang arguing with the two men about owing money. The restaurant worker told police Yang told Hingorani, "I paid your uncle the money."

The revelation of the deadly gambling debt dispute was contained in an Oct. 27 police application for a warrant to search the cell phone records of Yang and Hingorani. Investigators want to confirm calls the men said they'd made or received on the day of the shooting.

Hingorani told police when Yang insisted the debt was paid, Hingorani called his father and handed the phone to Yang so he could directly explain his claim.

On the day of the shooting, Yang told police he had received a threatening message on his cell phone saying "people would be coming to the restaurant to kill him," according to an investigator's statement supporting the search warrant.

Instead of calling police about the threats, Yang put a .357 magnum revolver in his pocket along with 13 extra bullets, according to the police statement.

As Yang was working on his laptop in the restaurant about 3:30 p.m. that day, he said the two men entered and attacked him. Yang told police the tall man choking him was Running Bear. He said the second man, described as east Indian male, grabbed him from behind.

Yang told police he got his gun out and shot the man choking him. The second man, Hingorani, ran from the restaurant.

Yang, who is 5-foot-2, 140 pounds, said he feared "they would kill him."

Police have described Hingorani as a "witness" in the slaying.

The restaurant worker said she was in the kitchen when she heard Yang yell, "Do not intimidate me" and "Do not touch me." She stepped back into the dining room and saw Yang yelling at the "tall man," an apparent reference to Running Bear.

The worker stepped back into the kitchen and heard a gunshot, according to the police report.

She looked back into the dining room and saw Yang "slightly bent over and pointing toward the ground." She then heard two more shots and saw the east Indian man fleeing the restaurant.

A man eating lunch told police he heard a "pop" and looked up to see a short man extending his arm and he heard several more "pops."

After the shooting, the customer recalled Yang saying, "He is a big guy. He came after me."

Asked about Yang's claim that he acted in self-defense, Denver District Attorney spokeswoman Lynn Kimbrough said, "Those are the kinds of issues that we let juries decide."

Running Bear, who was 6 feet tall and 220 pounds, had a history of arrests in Denver on charges of assault, car theft and clashing with police. In April 2009 he was convicted of assault and disturbing the peace. He was also convicted in 2007 of refusing a police order, and in 2002 for assault and disturbing the peace.