OMAHA, Neb. (AP) — Investigators long suspected two known criminals were responsible for a shooting that killed two Nebraska lawmen in 1937.

But it wasn’t until 80 years later that the case was re-examined when one of the suspect’s sons told investigators he, too, believed his father was responsible.

The Nebraska Attorney General’s Office announced Tuesday investigators consider the case solved after a three-year effort that included tracking down decades-old case files.

The office says evidence shows that the two suspects — Marion Cooley and Charles Doody — shot Boone County Sheriff Lawrence Smoyer and County Constable William Henry Wathen outside a farm near Albion on June 17, 1937.

The lawmen were ambushed while investigating a suspicious vehicle. Smoyer died instantly. Wathen died 108 days later.

Cooley died in 1965, and Doody in 1995.