TUCSON, Ariz. (AP) _ When Patrick Zanzucchi left a topless bar early Tuesday, a man wearing a ski mask tried to rob him. Shots were exchanged and the masked man was killed.

More than two hours later, officers identified the dead man as one of their own. Now, they think he may have been involved in a series of heists since 1992.

``In my 28 years as a police officer, I have never seen more blatant, rogue behavior,'' said Tucson Police Chief Douglas Smith, who said he was ``disgusted and embarrassed'' by the case.

Gabriel Abendano, a 41-year-old off-duty undercover vice officer, was shot once in the head as Zanzucchi defended himself from the robbery, police said.

Zanzucchi, who lives in Phoenix, was not charged, Smith said.

Abendano's badge and ID were found in the trunk of his department-assigned car, along with about an ounce of marijuana, Smith said.

Abendano ``was hooded, wearing dark clothing, wearing body armor, he had duct tape on the bottom of his shoes and a tape-recorder taped to his chest,'' the chief said.

``He was driving a take-home vehicle as part of his assignment to the vice unit; the license plate was removed.''

Smith said he was ``sickened and disgraced to report ... the blatant criminal conduct of an officer.''

``I'll tell you flat-out. We believe that at least the description is consistent with a series of robberies dating back to '92,'' the chief said, including at least five holdups, all apparently tied to night clubs, bars or restaurants.

Abendano was a police recruit briefly in 1978, worked as an officer in Mesa from 1984 to 1986, then was hired by the Tucson Police Department. He resigned for personal reasons in 1993, was rehired in February 1994 and had worked as a vice officer since September.

Smith, who announced a series of internal changes Tuesday in hopes of restoring the department's reputation, said the case only further lowers police morale.

In the last year, eight officers and a civilian clerk have been named in criminal cases, including four involving sexual misconduct. Five were fired, one retired, one resigned and two are under suspension. Another seven officers are under investigation.