That is despicable. The Zoo shouldn't allow people to torment its animals like that.
There's a nice little Zoo out in So California.. the Santa Barbara Zoo. Their gorilla exhibit is enclosed with strong plexiglass, viewable only from a downstairs room - so people can respectfully view the beasts without disturbing them. There is also plenty of private areas for the gorillas to retire to when they tire of being viewed by the zoo patrons.