It was a phone call urging renewed scrutiny of the unsolved 1937 killings of two eastern-central Nebraska lawmen that helped lead to a re-examination and solving of the case, Nebraska investigators said Tuesday.

But it wasn't the victims' family calling for a new look. It was the son of one of the suspects.

"He called me in late December 2014," Seward County Sheriff Joe Yocum said. "He had seen a story about the case that had appeared in Nebraska Life magazine. He was convinced that his father was involved in the killing of these men."

The Nebraska Attorney General's office is convinced, too, declaring the shooting deaths solved. Officials gathered for a news conference Tuesday in Albion to say Marion Cooley and Charles Doody — both long dead — had shot Boone County Sheriff Lawrence Smoyer and Boone County Constable William Henry Wathen outside a ranch near Albion on June 17, 1937.

That morning, Smoyer and Wathen were investigating reports of a suspicious vehicle parked at the ranch when they encountered two suspects who fired on the officers. Smoyer was shot in the head and died instantly in the ambush. Wathen returned fire, but was shot in both hips and left for dead. He was found the next day and lived another 108 days before succumbing to his injuries. Tuesday's announcement was made on the 80th anniversary of Wathen's death.

Wathen was able to give detailed accounts of the shooting, the suspects and their car and even the car's license plate. Within days, Cooley and Doody, who were already career criminals, had been identified as the top suspects.

The car used in the ambush turned out to have been stolen from Denver. It was later found in Cheyenne, Wyoming, riddled with bullets from Wathen's gun. Multiple sightings of the car and men matching the description of Cooley and Doody were reported. A plaster cast from the scene matched Cooley's footprints.

When Nebraska investigators were ready to issue an arrest warrant for the men about a year after the shooting, Doody was nowhere to be found, and Cooley was already serving a prison sentence in Colorado in an unrelated case. According to the laws at the time, Nebraska had to wait until Cooley was paroled in 1948 before Nebraska officials could take him into custody.

But by then, World War II had wreaked havoc on the case. The original investigators who would have served as witnesses had died or been killed in the war, were still in the military stationed at unknown posts or had retired to places unknown. A reorganization of the Nebraska State Sheriff's Association into what is now the Nebraska State Patrol saw the shuffling of files in the case that weren't found again until sometime in the last three years.

And as the years marched on, Cooley and Doody — who used the alias Charles Simms — served time in prisons in Colorado and California for various crimes. Officials say Cooley had no known children and died in 1965. Doody, living as Simms, married at least a couple of times and had several children, including the son who called Nebraska investigators in 2014. Doody died in 1995.

Yocum said he and state attorney general chief investigator Bill Black, who is originally from Albion, learned sometime in 2014 that they had both been occasionally investigating the case on their own. They began exchanging information on the case when Doody's son called.

Yocum and Black then began poring over old files in the case whenever they had time aside from their other cases, piecing together long-buried notes, files and evidence to confirm what investigators 80 years ago had believed — that Cooley and Doody were responsible.

Prosecutors reviewed the work against modern prosecutorial standards to close the case, said Suzanne Gage, a spokeswoman for the Nebraska Attorney General's Office.

"If these men were living, they would be charged and, we believe, would be held responsible," she said.

Yocum said he spoke to Doody's son a few days before Tuesday's announcement.

"He said he didn't want to be contacted by media," Yocum said. "All he wanted from me was any newspaper articles or any stories that were written in the local media. He also wanted me to extend an apology to the families of the deceased."