I'm laughing because I've shot through the windscreen of an old junker with a BB air rifle. Anyone who claims a normal (i.e. unarmored) car windshield or door panels will stop a 9mm P is seriously full of soup.
You've got a second-hand account from a LEO above, which I quoted. Ive got several similar accounts; both first and second hand.
Not sure what sort of BB gun you were using and whether or not it may have been equipped with the rare "Lightspeed Muzzle Velocity" option but, under real world conditions, a 9x19 is insufficient to reliably expect windshield penetration unless you care to stand on the hood and fire straight on at a distance of three feet.
This is one of the primary reasons that the .40 is adopted by most law enforcement agencies.
No soup here. What have I to gain?