ARAPAHOE COUNTY — Vicki Carpenter was a beautiful, popular, energetic 24-year-old woman with a loving family and a 3-year-old son.

In February 1985, she decided to try some modeling. It’s what took her to Knicks Restaurant and Saloon in Tamarac Square for a modeling contest.

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She won the swimsuit competition and then left to meet friends at another nearby bar. She never made it there.

The next day her car was found at an apartment complex on Hampden Avenue, with a slit tire.

The slashed tire on Vicki Carpenter's car
The slashed tire on Vicki Carpenter's car

There was no sign of her until nearly two months later when her body was found in the Cherry Creek Spillway. It's a moment her little sister Michelle will never forget.

Divers recovering the body of Vicki Carpenter from the Cherry Creek Reservoir Spillway
Divers recovering the body of Vicki Carpenter from the Cherry Creek Reservoir Spillway

"I dropped the phone and fell to my knees on the floor, and I don't remember much after that," said her sister Michelle."But that kind of pain doesn't go away."

Whoever killed her had hoped that her remains would never be found.

"They weighted her body down with cinderblocks and chains in hopes that she would never be found," said Michelle. "What kind of person does that? It's a monster that would do that."

Chains that were used to weight down the body of Vicki Carpenter
Chains that were used to weight down the body of Vicki Carpenter

Now 33 years later, cold case investigators are still trying to figure out who killed Vicki.

There have been many theories over the years. One theory was that someone might have seen her at the swimsuit competition, followed her and attacked her. They speculated that an ex might be responsible, but none of the theories have panned out.

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The condition of her remains caused problems for investigators who have never been able to determine her exact cause of death. There also was no DNA evidence.

A missing persons poster for Vicki Carpenter
A missing persons poster for Vicki Carpenter

One witness came forward and told police she saw Vicki after she left Knicks, at a 7-11 on East Girard Avenue. That person said Vicki was with another woman with long dark hair. The mystery woman has never been found.

RELATED : Unsolved: Patricia Louise Smith was bludgeoned to death in 1984

Vicki's family says knowing who killed her all those years ago would offer some justice and provide answers for the son who never really got to know his mother.

Vicki Carpenter
Vicki Carpenter

"She was a beautiful 24-year-old, wonderful woman, but she was also a little girl, somebody's little girl, a sister, a mom, a grandchild," said Michelle. "When they took her away, part of us died with her."

All this week at 6 a.m., 9NEWS is looking at Colorado Cold Cases and where these unsolved murders stand today.

On Monday, we featured the case of Patricia Louise Smith. The 50-year-old mother and grandmother was killed in 1984. Her killing was linked to several other crimes, including the brutal slaying of an Aurora family. None have been solved. Watch her story below.

On Tuesday we featured the case of Jane Doe who was found dead in 1993. Watch her story below.

On Wednesday, we featured the 1986 murder of Richard Van Duyn. He was delivering money bags to an Aspen park bank when he was shot and killed. Watch his story below.