Here's a good principle in life: Leave other people's sh*t alone! It's not cute, it's not a prank, it's not hilarious. It's other people's property. In the state of Texas you can use deadly force to protect your car. You can shoot as you approach or as they attempt to drive off or anything else that they might be doing in or on your car.
Perhaps if more states adopted a similar policy more people would remember to leave other people's stuff alone.
OP, sorry to hear about this.