Clifford Eagle strolled into Billings, Mont., police station on April 18 and told police that he wanted to get something off his chest.
At around 10:30 p.m. as one of the officers was leaving the station house, Eagle allegedly told authorities that a quarter century ago, when he was 28 years old, he and another man got into a heated argument with a third man in Oklahoma about property, and he ended up shooting the man dead, Fox23.com reported.
He was then interviewed at the station and authorities in Oklahoma were alerted. The Billings Gazette reported that he stayed voluntarily until officers made the arrest.
Eagle, who is being held at the Yellowstone County Detention Facility, declined a phone call from FoxNews.com.
The 1987 murder of Leo Reasnor, the long-time county commissioner had shaken the community of Lequire, Okla.
Reasnor, who was 49 at the time, was shot dead on a rural stretch of road he owned. His son-in-law found his body inside his pickup truck with a gunshot wound to the head, and while at one point the killer's arrest seemed imminent, the case eventually went cold.
But just because an investigation may putter out, seldom do the emotions of a victim's family.
"There is not a day that goes through my mind that I don't think of my Daddy. Never,” Kim Stout, Reasnor's daughter said. The family keeps a scrapbook of all the local newspaper articles detailing his murder.
Eagle was convicted in Oklahoma of a child's rape in 2003 and released in 2007. He was then required to register as a sex offender, the Billings Gazette reported.
He allegedly told investigators that he was with another man during the argument and the two thought Reasnor had a gun, so they fired. Eagle implicated Vince Johnson in the shooting, but Johnson was executed in Oklahoma for another murder in 1991.
"Being able to reach a conclusion on a case even 25 years later, it brings a lot of hope for people who haven't had their case solved," Stan Florence, the director of the Oklahoma State Bureau of investigations said.
Eagle is facing a first-degree murder charge. He is awaiting extradition to Oklahoma.
"It would have not taken me 25 years to be burdened to the point to confess but maybe it just took him that long," Phyllis Reasnor-Arnett, Reasnor's widow said.
Fox News' Edmund DeMarche contributed to this report.