66-year-old Jack Pursel walked into the Waterloo Police Department and admitted to the murders of Robert and Goldie Huntbach.
Investigators say his faith made him travel from California to Iowa to confess to the crime in person.
"He became a Christian," said Dan Trelka, Waterloo Director of Safety Services. "He said he needed to cleanse his soul by confessing."
Pursel is charged with two counts of murder in the first degree, each count carrying a life term. Bond was set for one million dollars on each count.
Captain Tim Pillack says Pursel admitted going to Robert and Goldie Huntbach's home on January 12, 1981 with the plan to rob and kill them.
"It's always rewarding, especially in a case like this, when we can solve something that in all probability was never going to be solved," said Captain Pillack.
Many of the couple's family members have either died or left the area.
Robert's nephew, George Huntbach, still lives in Waterloo.
He says he thought about the case just last week. Huntbach said Wednesday's arrest made him "sit up and take notice."
Huntbach remembers his uncle's death vividly.
In 1981 their murder made headlines -- and weighed heavy on the minds of nearly everyone in Waterloo.
"It was a big case for the police department and it was a big case for Black Hawk County," said Pillack.
Police were never able to formally answer the question of who committed the crimes.
"Sometimes when you have a suspect, it doesn't necessarily mean you have enough probably cause to make an arrest. In this case, that's what happened. And that's why it went unsolved for so many years," Pillack noted.
After several years of investigating, they were forced to put the case on the shelf -- literally.
"We keep all cold cases. We have, we call it our homicide room," Pillack explained.
And that's where it sat for decades until Pursel walked into the Waterloo Police Department.
After nearly 30 years of storage, officers were able to pull the box of evidence out, and revisit the crime.
"That's exactly what we did. We got the old case out and started to review the reports of officers who worked the case in 1981," Pillack said.
They reviewed Pursel's version of the murders with the evidence, and talked with retired investigators.
While it seems too good to be true, it appears they finally have their man.
"He has told us some things that only somebody directly involved in the case would be aware of," Pillack said.
Why Pursel came forward after 30 years is still not clear, but after all this time, his confession is giving a lot of people peace of mind.
"Obviously I'm sure he has his own personal reasons to come forward. To be honest with you, we're just glad he did. Obviously a case this old, we don't get leads on that very often. I'm sure the family is probably relieved to know this case has finally ended with an arrest," Pillack added.
Pursel has a criminal history on the west coast including convictions which resulted in his placement on the California list of sexual predators.