DENVER (KDVR) — There are hundreds of unsolved homicide cases, long-term missing person cases, and unidentified remains cases in Colorado where at least three years have passed since the crime happened.

The Colorado cold case task force created a list of those cases dating back to 1970.

Who killed Richard Elliott?

Richard Elliott was grocery shopping at Alfalfa’s market on April 17, 1999. When he left the grocery store, he walked to the parking lot and got into his vehicle in the store’s parking lot. The Denver Police Department said that’s when an unknown man walked up, shot Elliott, and left the area on foot.

Elliott’s murder remains unsolved more than 23 years later.

At the time of his murder, DPD said he was working for a small Colorado Springs computer company as a computer engineer.

If you have any information about Elliott’s murder, please contact the Denver Police Department at 720-913-2000. You can also provide an anonymous tip to the Metro Denver Crime Stoppers and be eligible to receive a reward up to $2,000.

Here are some of the other cases we’ve highlighted:

The National Missing and Unidentified Persons System shows there are currently 21,556 open missing persons cases in the United States and over 300 in Colorado.