The father of the man who choked to death in the lobby of Voodoo Doughnut on East Colfax Avenue early Sunday morning describes him as an "energetic and open-minded person" with an infectious laugh.

"It's tragic," Curtis Malouff said. "It's a loss of life that shouldn't be."

Travis Malouff, 42, died from "asphyxia, due to obstruction of the airway," the Denver Office of the Medical Examiner announced Monday morning.

Police and paramedics were first called to the doughnut shop in the 1500 block of Colfax at around 1:30 a.m. Sunday after receiving a report Malouff was choking.

The manager at the shop confirmed to 9NEWS a person died in their lobby, but wouldn't say anything else. Witnesses say Malouff was doing a doughnut challenge before he died.

The challenge is to eat a half-pound doughnut in 80 seconds or less.

Two people who were inside at the time say people rushed to help the man when they realized he was choking, but they couldn't perform the Heimlich maneuver.

"They tried so hard to do everything. It was clear that nobody was trained and they were just reacting," a witness said. "You [have to]do something I think."

Food challenges are popular throughout Colorado and come with rewards that range from bragging rights to free food for life.

Beau Jo's pizza offers $100 and two free T-shirts to any two people who can finish a 14-pound pie. While Jack-n-Grill offers free food for life to any woman who can finish its seven-pound breakfast burrito.

Denver Police say Malouff's death does not appear to be suspicious, but they won't say anything more than that.

Voodoo released a statement saying the company is saddened by what happened and is cooperating with police.

Curtis Malouff says everyone remembers his son's smile, energy and laugh.

"If a challenge is there -- he'd probably take it," he said.

Travis is survived by his father, Curtis, mother Kay Malouff and brother Ferris Malouff.