They believe he's specifically looking for women going in to the gym without purses.
Police say the crime spree stretches from Southlake to Plano, but six of the locations are in Flower Mound.
Melissa Pace had her car broken into last week while she worked out at a Lifetime Fitness in Flower Mound. She'd left a tote bag in her Escalade with her credit cards and driver's license.
"Lifetime has cameras, and so I thought, ‘Who in the world is going to do it?' because there are cameras all over the place, but I was wrong," said Pace.
Police believe the same suspect was caught on security camera video taken after another smash-and-grab spree at a Lifetime Fitness in Colleyville as the suspect used a stolen card at a nearby Hobby Lobby.
Colleyville police call the man a dedicated opportunist who's watching for women who get out of their cars without a purse.
"He knows what he's going to do, where he's going to strike," said Assistant Police Chief Robert Hinton with the Colleyville Police Department. "He's going to take the opportunity to see who has left their valuables in the car and then he's going to strike."
Flower Mound police have reported six similar crimes since November.
They're convinced that the thief is using a spring-loaded punch to break out windows.
Police also released pictures of the man and the white Ford SUV he was seen leaving a parking lot in.
Plano, Grapevine and Southlake are also looking for the suspected smash-and-grab thief, and all the departments warn not to leave valuables in cars.
Anyone with information on the suspect is asked to call the Flower Mound Police Department's tip line at 972-874-3307. Callers can remain anonymous.