My late dad was a police and I actually remembered him talking to his fellow police friends about the same exact situation. He stopped a suspicious looking car with tinted windows. Asked the driver and the passengers inside to lower the window. They lowered it but not completely, only showing their head. Definitely hiding something under the window. My dad just let it slide before calling for reinforcements. Turns out they're a gang of robbers with guns. For context, I don't live in USA and civilians don't have guns.