Castle Rock police are looking for a police impersonator who apparently has been out trolling the streets for weeks.

Officers say he's been spotted along Founders Parkway near Highway 86 in a car that could be mistaken for an undercover unit. He's pulled over at least three vehicles and asked for personal information, police said.

The latest incident occurred on Sunday night, when the man pulled a woman over to issue her a "verbal warning." The fake officer said that he didn't have time to write her a ticket, but he jotted her personal information down and warned her to slow down, Castle Rock Police Detective Troy Stembel said.

Officers worry that the impersonator is becoming brazen since his previous sighting on Sept. 4. During that time, the man turned on his red and blue flashing lights and tried to pull over an off-duty Castle Rock firefighter, Stembel said.

The firefighter didn't think it was a real police car behind him so he refused to pull over, Stembel said. However, he did give officers a good description of the impersonator's face and cited several numbers on the man's license plate.

Castle Rock police have increased their patrol along Founders Parkway since the first reported incident in May, Stembel said.

The vehicle police are searching for is a 1999 dark blue Crown Victoria with red and blue dashboard lights, which could be mistaken for a police car at night. It has Colorado license plate number 122JSB.

The man is described as Hispanic, in his 40s with a possible mustache. In each case, the imposter wore a dark shirt and blue jeans. In the May and September incidents, he also wore a straw cowboy hat, and on Sunday he wore a baseball cap.

Police say a real officer would never approach a vehicle wearing a cowboy hat and jeans.

Castle Rock officers wear a black uniform with a fully loaded belt. Badges are pinned on the left breast of the uniform with name tags on the right side, Stembel said. Douglas County sheriff's deputies and Colorado State Patrol troopers wear light blue uniforms.

If you are being pulled over by an unmarked car, police say continue driving to a well-lit spot where you can crack your window to ask the officer to show his badge or call the police on your cell phone to verify if the officer is legitimate.

Impersonating a police officer is a felony, punishable up to $100,000 in fines and an eight-year prison sentence.

Anyone who thinks they have been approached by a cop impersonator on Founders Parkway is asked to call Castle Rock police at (303) 663-6100.