From USA Today:

OAKLAND, California (AP) — Oakland police say a man impersonating a police officer tried to pull over a real undercover officer and was arrested.

Police say 21-year-old Antonio Fernandez Martinez of Oakland was arrested Wednesday in the Fruitvale district after trying to pull over an unmarked police vehicle. Martinez was driving a Ford Crown Victoria outfitted with flashing lights, a microphone and speakers.

Martinez, a convicted car thief, will have his felony probation revoked and could face a prison term.

The officer, Jim Beere, says Martinez probably thought he'd be an easy mark to rob.