On March 16, 1949, Detective William O'Brien was shot and killed while making a routine check on the Franklin Load and Mercantile pawnshop at 1400 Franklin Avenue. As he entered the shop he interrupted a robbery which was taking place and was shot in the chest. The two suspects then shot and wounded the owners before fleeing with stolen property. 

Both suspects were later apprehended, convicted of murder, and sentenced to life in prison.

Detective O'Brien was assigned to the Tracing Bureau and had been with the agency for 31 years. He was survived by his wife and three daughters. Interred: Cavalry Cemetery.