An unmanned Cochise County Sheriff's patrol vehicle parked at a Sierra Vista dealership as a security measure was vandalized Monday night, authorities said.

A rock, found inside the vehicle, was used to smash the rear window, and the side mirrors were damaged. There also were large dents on the doors and  destruction that occurred using a type of pipe or bar, said Carol Capas, a sheriff's spokeswoman.

The damage estimate had not been determined.

The vehicle was parked at Lawley Nissan, 2960 E. Fry Boulevard, at the dealership's new building that is under construction. The unmanned vehicle was part of a security measure, Capas said. 

At about 10:30 p.m. Monday, a Sierra Vista police officer reported the damage while doing a security check. The patrol vehicle was parked facing the dealership. The damaged vehicle was removed by sheriff's personnel.

The investigation is being handled by Sierra Vista police. Anyone with information is asked to call the police department.

Contact reporter Carmen Duarte at cduarte@tucson.com or 573-4104. On Twitter: @cduartestar