Investigators say on the night of May 11, the suspect flashed his high beams and a white strobe light before lightly bumping the victim's car from behind, causing the driver to pull over near Sunflower Avenue and the 210 Freeway.
The suspect brandished an oval badge and asked to see the driver's license.
The driver had been drinking, but the suspect told him he'd cut him "a break" and just take him to the victim's sister's home in Glendora.
Once at the home, the suspect introduced himself as a police officer and said he would just let the victim off with a warning, even telling the sister and her husband "you don't know me" and "this never happened."
Five days later, the suspect went back to the sister's house, claiming he was there to check up on the victim. When the victim's sister turned away from the front door briefly to tend to her children, the suspect let himself in. The woman said it appeared the suspect wanted to get her to the back of the house.
At one point, authorities said the suspect touched the woman on the arm and leg, making her feel very uncomfortable. When the woman said her husband would be home soon, the suspect left immediately.
The suspect was driving a cream-colored Ford Edge with tinted windows, chrome rims and paper plates. He was described as a white man in his 40s, slightly over 6 feet tall, weighing about 250 pounds, with blue eyes and gray spiked hair. He was clean shaven.
The badge he showed to the victim was described as a shield-type badge with a leather backing and blue lettering across the top and a black stripe going horizontally across. He also had a black semi-automatic pistol in a flat black holster on his right hip.
Police fear the suspect's bold move could lead to more aggressive behavior.
"Our concern is we don't know what this man's intentions are or who he is, and we want the public to be aware," said Lt. Brian Summers with Glendora police.
Authorities are not ruling out the possibility that the suspect may belong to a police agency and that he's doing these things while he's off duty.
If you have any information, you're urged to call Detective Jason Tibbetts with the Glendora Police Department at (626) 914-8250.