The place I volunteer at strictly forbids people from just coming and walking around without escort. (We've got tigers, too, but even the smallest animals there will gladly rip your face off.) If you're a visitor there, a volunteer has to be with you at all times. (Guided tours only, with rules clearly explained and also a signed agreement to those rules.) People still manage to be stupid, though, which is why I decided to only volunteer there on the one day of the week it's closed to the public.
BTW, the suits make those guys look like mobsters. (Not quite. You're supposed to wear a tie. If you don't have a knot style memorized, you can always find instructions on the internet and print them out, so there's no excuse.)