Now 78, Dryman was arrested Tuesday by police and is awaiting extradition to Montana.
Dryman was sentenced in 1955 to life in prison. He was paroled in 1969, and three years later, he disappeared. No Montana offender had been missing longer.
Clem Pellett is the victim's grandson. The Bellevue, Wash., surgeon says he pursued the killer to fill a hole in his family's memory.