Ann Arbor police detectives released a computer-generated sketch this morning of a man they said robbed O'Reilly Auto Parts on Tuesday night.

About 9:10 p.m., police said the man entered the business on West Stadium Boulevard through an unlocked back door after it closed.

He pointed a handgun at a 26-year-old female employee, police said, and demanded money. The man grabbed cash from the register and left out the back door.

He was described as white, 5 feet, 4 inches tall, thin, with blond hair and glasses. He was wearing a dark blue sweatshirt with the hood pulled up, dark jeans, black gloves, and was carrying a bag.

Anyone with information can call the police department's tip line at (734) 794-6939.