Policeman Costello was shot and killed as he and his partner made a traffic stop. When Policeman Costello made contact with the driver the man pulled a gun. As Policeman Costello backed away his partner and the suspect exchanged shots. Policeman Costello was shot in the chest during the exchange. The suspect fled the scene but was arrested the following day with a gunshot wound to his knee.
The suspect, who was charged with first degree murder, was tried and acquitted.