A two-part investigation. Brad stands near a car (as you can see in the trophy picture) regretting what he may or may not have done. He certainly can't remember, so Ronan takes it upon himself to try and ease the poor soul's mind. Start the investigation by exploring the immediate area surrounding the car (license plate, broken bottle of whiskey, purse with receipt) and you will be directed to proceed to the gas station.
There, you'll find three residual memories for the other people in the car: Rick, Brad, and Jenny. These are the only clues you will need to finish the question, and obtain another clue. Use that clue "Mysterious Bang" on the gas station attendant fixing the door to solve the mystery, then return back to Brad to complete his task. (You do not need the other two clues for anything, not even another trophy. However, should you still want it for completion sake, they are located near the Police Station from the Gas Station and are a dinged can and bits from a broken reflector on the ground near it.)