(CNN) -- For Clem Pellett, tracking down his grandfather's killer was not his original mission. 

"I was just putting together an old family story ... and these serendipitous events happened, and we accidentally caught him," Pellett, of Bellevue, Washington, told CNN in a phone interview Wednesday. 

That "old family story" focuses on two men: Clarence Pellet -- a grandfather that Clem Pellett never knew -- and a drifter named Frank Dryman. 

According to the Montana Department of Corrections, on April 4, 1951, Clarence Pellett picked up a hitchhiker near Shelby, Montana. The hitchhiker was Dryman, then a 19-year-old drifter who was carrying a loaded gun that, according to the state, he used to shoot and kill Clarence Pellett on the side of windswept Montana road. 

Dryman took the car and drove to Canada, where he was later arrested for the murder, according to the Montana Department of Corrections. 

After several trials and appeals, Dryman was convicted in Montana and sentenced to life in prison, then paroled in 1969, according to state records. Less than two years after his parole, Dryman was listed by the Montana Department of Corrections as "absconded." He had disappeared. 

And that is where the "old family story" stopped for nearly 40 years, until last year when Clem Pellett came across some old newspapers clippings of the murder, which had occurred two years before he was born. 

"So what I knew of it (was) 'never pick up a hitchhiker,' and 'your grandfather died begging for his life,'" he said. 
Was he convicted?
After several trials and appeals, Dryman was convicted in