This is a very difficult "case" and it raises complicated moral dilemmas that reach to the very core of ethical reasoning, jurisprudence and philosophical considerations. It also raises the issue of whether we should have zoos at all, in which animals are held to be oggled at by humans. There is a valid argument that the artificial environment of a zoo can protect endangered species that would go extinct in the wild - raising their numbers artificially so as to perhaps reintroduce them back into the wild at a later stage.
Yet this case shows the corollary: it may have been better for Harambe never to be kept in a zoo in the first place. Had he not been, this beautiful creature may still be living, freely roaming around out there in the wild, instead of dying in these tragic circumstances.
Now to the situation at hand....
A perfectly innocent, vulnerable child found himself placed in a
potentially life-threatening situation. In fear of what could have transpired, zoo keepers made a snap decision - out of instantaneous fear for the child's life - to shoot and kill a gorilla belonging to an endangered species, who had been much loved by everyone - including the zoo keepers.
As others have argued, I first wish to say that I am incredibly incensed at the gross negligence of both the parents and whoever constructed the holding pen. The parents clearly failed in a duty of care towards their child, who should have been under round the clock supervision while in the zoo. Something like this should have been foreseeable to happen based upon the curious nature of many little boys - and to this end I also attach significant blame to whoever constructed the holding pen for not making it more secure.
The parents, as I see it, by means of their gross negligence have indirectly led to the death of an animal belonging to an endangered species. Their inaction as regards their child was reckless.
In terms of this debate over the worth of human lives compared with animal lives...
Let me first make an arguement that does not rely on "species" distinction in the hopes of transcending the gulf between posters here on this issue.
This is an arguement I will call the "criterion of vulnerability". To understand it, you only need to consider the saying attributed to Jesus:
"The least among all of you is the greatest"
If we apply this statement to ethics, we are left to conclude that our innate sense of justice should always place greater moral value on the side of those deemed to be the more vulnerable and helpless in any potentially dangerous situation, where the weaker party is exposed to the possibility of proportionately greater harm if action is not taken on his/her behalf.
Consider this: if you were to see a small, defenceless Labrador puppy potentially about to be set upon by a hyena, whom would your natural sense of compassion orient towards?
If you do not answer "the puppy," then I would say there is something deeply wrong with your ability to experience empathy.
We have a natural disposition to accord greater moral value and security to whatever being is deemed more vulnerable in a given relationship or situation.
Thus, I think that no moral blame can be attached to the man who fired the shot at the gorilla.
This was a giant, fully matured, adult gorilla.
The child was placed at a massive disadvantage on account of his diminutive size, unawareness of the potential danger faced and so forth.
Therefore in this situation, quite apart from anything to do with species distinction, and whether or not the gorilla actually was going to cause grievous bodily harm or death to the child, I believe that the zoo-keeper had an innate moral obligation to do everything in his power to make sure that the more vulnerable party in this situation - the child - remained unharmed.
That he had to kill a beautiful, large animal belonging to an endangered species to evade that ghastly possibility, is a colossal tragedy indirectly attributable to the negligence of the child's parents.
But the zoo-keeper had to act. Placed in the same situation, irrespective of my genuine feelings of remorse for Harambe, I would have done the same. I don't think I'd have even thought about - it would have been an instinctive, instantaneous desire to protect the more vulnerable party at all costs.