The 12-year-old stepson of an Alexandria police officer was accidentally killed yesterday morning by a bullet from his stepfather's .38-caliber service revolver, police said.

A spokesman said police, responding to a telephone call about an accidental shooting, found John Joseph Staus at his apartment home in 5300 block of Duke Street suffering from a gunshot wound in his upper right chest.

Staus' stepfather, William R. Trotti, an 11-year veteran of the Alexandria police force, was in the apartment at the time, a prosecutor said.

A preliminary investigation blamed the shooting on an accidental discharge of Trotti's revolver, said Lt. Joseph Hilleary of the criminal investigation division.

Police and the Alexandria commonwealth's attorney's office, which were investigating the shooting, declined to provide details of the shooting.

Staus was taken to Alexandria Hospital, where he died.

Under Virginia law, a police officer is authorized to take home his service revolver, said Sgt. Ralph Stanley, another member of the criminal investigations division. "He's on duty 24 hours under Virginia state law, so he has to have his credentials and weapons with him," he said.

Stanley said he wasn't aware of any city policy on how Alexandria officers should store their revolvers at their homes.