He was survived by his wife and daughters.
Detective O'Brien was shot while making a routine check on a pawnshop. 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. Detective O'Brien was taken to City Hospital where he died upon arrival.
Both suspects were later apprehended, convicted of murder, and sentenced to life in prison.
There are currently no tributes for Detective William J. O'Brien.