BUFFALO GROVE --Police in northwest suburban Buffalo Grove are looking for a man who impersonated a police officer and then tried to abduct and sexually assault a woman. It happened around 5 o'clock Saturday morning as the woman was driving on Thompson Boulevard near Arlington Heights Road. Investigators say a man driving a silver, four-door Audi stopped her vehicle and identified himself as an undercover officer. He handcuffed the woman and put her in his car. The woman was able to run from the car. But the man tackled her and tried to sexually assault her before fleeing the area. The suspect is described as a white male in his mid- to late-20s, 180 - 109 pounds, with short, brown, spiked hair. Buffalo Grove police say drivers should call 911 immediately if an unmarked vehicle is making a traffic stop. The victim thought the man behind her was a police officer trying to make her pull over. He was in an unmarked car, dressed in plain clothes but flashing his lights at her. "He came to the driver's side door and identified himself as a police officer, and from there he asked to see their I.D.s," said Todd Kupsak, police spokesperson. The man told the victim's friend, who was with her, that she could leave. Then he put handcuffs on the driver and took her to his car. After driving a short way down the street he took the cuffs off and put her in the front seat. That's when she became suspicious. "She then at that time felt, there's no way this is a police officer and opened the door and fled. He chased after her, tackled her," said Kupsak. "She started screaming, moving around, flailing, got up. He then, the offender, got up and just left." Police say it should be clear how to identify a real police officer. "It's not common practice for police departments to be pulling people over on routine traffic stops in unmarked vehicles," said Kupsak. Police say if you have any doubt as to whether it is a real police officer who has pulled you over, you should drive to a well-lit area before you pull over and call 911 and ask them to send over more officers. They say if they find the suspect he could be facing charges of kidnapping and sexual assault.