Police said 63-year-old John Kelly Gentry Jr. murdered a woman in Michigan and a man in Ohio in April 1983.
Authorities said Gentry, who at the time was 30, was suspected of killing 25-year-old Barbara Gerber in her home.
Her brother found her body and called police. Authorities discovered her car had been stolen and later found it in Toledo, Ohio.
Detectives identified Gentry as a suspect in Gerber's murder and began searching for him in Ohio. They searched a rare coin store owned by William Veith and Veith's body was found in the basement.
Authorities also discovered Veith's car was stolen.
His car was later found in South Bend, Indiana, authorities said. Gentry was identified as a suspect in Veith's murder as well.
Authorities believed Gentry had a relationship with both victims.
Detectives said Gentry's last form of contact was two postcards sent out a month after the murders. One was sent from San Diego to a friend, and the other was sent from Los Angeles to his father.
Police released old photos of Gentry and an age-progressed image of what he may currently look like.
Detectives urge the public to contact authorities with any information by calling Det. Jeff Smith at (734) 240-7530.