They should of called in Bill Cosby to sedate it (no harmful intentions, it may have actually happened)
A high glass window should be fixed around the enclosure for everyones safety and pleasure of viewing.
Secondly letting a child wander off at a zoo wouldnt really qualify you to sue if the kid clambered over the rail, if you were there then it most likely wouldnt have happened.
Third to the animal rights groups, zoos are not corporate enterprises (to my understanding) and lots of money goes into housing, entertaining, breeding and feeding the animals. Also a human life is more valuable to the state than a gorilla, and there was simply no time for tranqing the ape due to the fact that it was gettjng agitated , defensive and a sharp prick might just really tick it off and having a dead gorilla and child would really hurt the zoos reputation, and lawsuits means less money for ensuring the animals have a comfortable life.
That is just my 2c on the arguement. It is sad yes and many parties can be blamed but more importantly it must be avoided in future
I think you are incorrect about your second point, you wouldn't believe what liability case law will allow suits for. Allurement or attractive nuisance come to mind, which is basically the principle that if there is something attractive to children on the property that is meant not to be trespassed on, it is the job of the property owner to make sure the property is safe as children cannot be blamed for their curiosity of something that is intriguing. I think the mother will owe some contributory negligence though, however that will literally be a % deducted off the settlement, which I believe is max 25% in Canada.
Otherwise I agree with you, other than the fact that they may be a corporate enterprise, that I don't know for sure, wouldn't really blame them if they were, everyone gotta make a buck.