A Maryland man posing as a police officer turned his lights and sirens on behind a real police officer, officials said.

John Vincent Angelini, 51, of Baltimore, was arrested Wednesday after Montgomery County police said he trailed an off-duty detective driving on the Intercounty Connector in an unmarked car.

The detective was headed eastbound on the ICC near Georgia Avenue about 8:15 p.m. Wednesday when he saw a car alongside him. It was a Ford Crown Victoria that looked like an unmarked police car, police said.

The driver of the Crown Victoria then slowed down so that he was behind the detective's car and turned on his siren, police said.

"The detective felt like he was being pulled over, began to reduce his speed and pulled over to the side of the road, at which point the Crown Victoria abruptly changed lanes again and continued past him," police spokesman Officer Rick Goodale said.

The detective then turned on his own lights and siren and stopped the driver near Layhill Road. He approached the Crown Victoria and saw it had red and blue lights on the grill and multiple antennas, police said.

Inside, the car had a radio microphone, emergency lights and switches, a dashboard-mounted camera and other police gear. The detective determined that Angelini was not an officer and arrested him.

"By activating his siren, he represented his vehicle as an emergency vehicle, and he's not authorized to do that," Goodale said.

He was charged with impersonating a police officer and released after posting $2,500 bond.

Anyone who believes that Angelini misrepresented himself to them as an officer is asked to call police at 240-773-6370.