Do you think I should have...?

OK, so I saw a guy park his car, throw a pop can and a cigarette out his window, leave his windows open and get out with a Marlboro box in his arms, and walk into a tobacco shop. So automatically i thought, 'Ooo...perfect oppertunity. I'll just go throw the pop can back into his car, kind of like in-your-face.' Well, first of all, I was with two other girls and we're all under 17 and I thought against it. For one, he could see me do it and come out to find three young girls in a parked car. Second, I thought it might be against the law. Is it?