He wore a uniform. He carried a radar gun. He drove a patrol car. He stopped traffic offenders.

There was just one little problem: Keith Ungerer is not, was not and probably never will be a police officer.Ungerer, 21, turned himself in Saturday after conducting his own patrols in stolen police cars for two weeks, Suffolk County police said.

He told investigators he "just wanted to help out," said police spokesman Salvatore Yovino. "He's a cop buff."

Ungerer's interest in police work crossed the line when he obtained spare keys to several Suffolk County police cruisers, Yovino said. Embarrassed police were not saying how he wound up with the keys.

Wearing an authentic looking uniform and toting a stolen radar gun, Ungerer began stopping traffic violators in the cruisers. "He'd just turn on the lights and pull 'em over," Yovino said.

Motorists who felt fortunate to get off with just a warning never realized the cop that pulled them over was a phony, Yovino said. Ungerer, who is unemployed, refilled the gas tanks before returning the cruisers to the police parking lot.

His undoing was answering radio calls. Sergeants in two precincts in the Long Island county compared notes on the "new officer" they kept seeing, Yovino said.