Roll up windows, lock doors, turn on windshield wipers. This scam was rampant in L.A. in the 1980s.
A guy did exactly what you said, and they snapped his wipers off his truck. He parked highly upset, and stepped out with a bat to confront the kids. One of them pulled out a handgun and shot the dude down right in rush hour traffic.
She lost her job, and the city started enforcing a no squeege ban.