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ST. CHARLES, MO (KTVI) - Police are asking for your help to find a gun used in at least six murders. They are offering a $25,000 reward for information leading to the arrest or conviction of a serial killer.

St. Charles City Police are still looking for the man who killed a young woman 24 years ago this May. He used a most unusual weapon that has been linked to five other murders. All along Interstate 70 in April and May of 1992.

The crime happened in the Boot Village Shoe store in the Bogey Hills Plaza on Zumbehl road at I-70. It was one of a series of murders that stretched from Indianapolis to Wichita, Kansas during the spring of 1992.

Authorities believe the killer stopped along the interstate and looked generally for women working by themselves. Nancy Kitzmiller, 24, who graduated from Oklahoma State University, matched his target.

A man in a nearby shop had a good look according to videos posted on the St. Charles CrimeStoppers website. At the time he was described as a white male in his mid-thirties, about 5 feet, 7 inches tall , slender to medium build with light brown to auburn colored hair.

Kitzmiller was found shot to death. The weapon, a long barrel semi-authomatic 22 caliber pistol known as an Erma Werke ET-22.

Police are asking gun collectors and dealers to notify them if they see such a weapon, or had one stolen in the early 1990s.

This is what the St. Charles Police Department posted to their Facebook page:

Attention Gun Enthusiasts, Take a close look at this flyer of a very unique gun. The firearm is an Erma Werke ET-22. This gun is believed to have been used to murder six shop clerks in the spring of 1992. Please share this flyer with any and all gun owners, collectors, and dealers. The killings occurred in shops located along Interstate 70 and Interstate 35 between Indianapolis and Wichita Kansas. This is also believed to be the weapon that killed Nancy Kitzmiller on May 4th,1992 in St. Charles at the Boot Village. The St. Charles Police Department needs your help to solve this crime!

The flyer states:

The killer may have stolen of acquired the weapon from the owner. The owner (or the killer) may have used corundum or red rouge for fire lapping of the weapon, or may have used corundum and rouge in grinding, polishing or machine shop work. If you know of someone who had this type of weapon in the spring of 1992, please call St. Charles Police at 1-800-800-3510.