Several drivers in Baytown returned to their cars to find broken glass and shattered windows.
Baytown police said the crooks scope out parking lots, look through windows when they see something valuable they smash the windows and grab it.
Robert Worthy said he's concerned about the crime.
"You got to be careful what you leave in the vehicle," he said.
A man said his brother returned to his car from working out at 24 Hour Fitness in the 3500 block of Garth Road to find the car had been broken into.
It also happened in the parking lot of a La Quinta motel in the 4600 block of the Eats Freeway, police said.
The crooks broke the windows of several vehicles and took electronics, money and other valuables, investigators said.
Worthy said he always keeps his possessions out of view of criminals when he goes to the gym.
"Every time I come and work out I don't leave anything in my truck," he said.
Baytown police aren't sure if the break-ins are related. They are still processing fingerprints taken from the vehicles.
Anyone with information is asked to call Baytown Crime Stoppers at 713-427-TIPS.