Quote Originally Posted by Miss Z
Over here vandalism would be the least of your worries. It's illegal to leave dogs in cars in the UK and you can get fined quite heftily. I think in many parts of the US, it's illegal too, but correct me if I'm wrong on this.

I agree with you that sometimes it affects those who had no intention of leaving them for long, but we have to be safe rather than sorry.
you are underestimating vandalism. It is illegal as well and you can be prosecuted.

I aggree with Lady's human. If you mean well and you are really concern with the dog inside the car and you believe that it could be in danger then call the dog warden/rspca/police/other authorities. No need to take the law in your own hands.