That is where I disagree with you. In this circumstance, I would, in fact put the gorilla's life above the 'alleged' danger to the kid's life. I can instantly think of at least five-six ways this situation could have been handled without harming either parties. That being said, even though 'prevention is better than cure' is cool and everything, I seriously can't digest the fact that Zoos aren't prepared for this kind of situation. It's like the lack of life boats on Titanic. I mean, come on man! Either put a 10 ft barrier around the enclosure or else have tranquilisers ready 24×7! If any of you are from India, you'd remember a recent case in New Delhi where a man was mauled to death by a white tiger. That was just sad and revealed the utter carelessness and lack of planning on the authorities' part. And let me remind you once again that the Tiger was agitated because the onlookers started pelting it with stones in hopes of shooing it away. Yes, I do blame the humans here too. I really think that the crowd entering the zoo should have a mandatory orientation lecture on what 'NOT TO DO'!
These are wild animals being kept against their will in an enclosure. Seriously, it's like turning a prison into a tourist attraction. Does that sound nice to you? Would you want to enjoy your evening with your family visiting a prison? When you think about it this way, it's almost sadistic. I've always hated Zoos. Even when I was a kid. Of course, I didn't have this much philosophy then, but something inside me just broke everytime I saw those animals.
My point is, if you're keeping a living, breathing being in a locked room, against their own will; a being who is just as much entitled to a natural habitat as a human; you are committing a crime against Nature. Did we evolve to Co exist? Or did we evolve to dominate? Keep all species in a natural habitat, and we are the weakest species on this planet. The only thing we have is a big brain which we use for selfish, self destructive purposes instead of finding ways to coexist.
Coming back to the original point, it was utterly wrong to kill the gorilla. If this kind of thing is okay, I believe it will be okay for me to kill a person who I think is going to harm my little baby brother. And don't give me the 'humans are different' stuff.... Humans are, in fact, more dangerous than these animals. The greatest acts of empathy I've seen or heard in my life have been performed by these so called wild animals. If you think it's right to kill them, then my friend, the one who is wild here is you.