The department closed the case after confirmation from the daughter of late Capt. Marion Thompson, who was also on the scene at the robbery, that her father had claimed to have shot and killed the robber who murdered his fellow officer.
After a chance encounter with Thompson's daughter Colleen Thompson Campbell, an Alhambra homicide detective reopened the case. Campbell told the detective that her father had been open about the fact that he fatally shot the killer of Nerison during a robbery in El Monte three years later.
It is unclear whether the new information presented new evidence that the slain robber had in fact been the officer's murderer.
The Alhambra Police Department honored Capt. Thompson at a recognition ceremony Thursday for solving the murder of Nerison almost 80 years before.