Exactly. This isn’t exactly a wild animal-he’s lived with people for 17 years. He’s also not some hungry tiger, he’s pretty close to being human and his keepers probably communicate quite well with him. I’m sure they could have gotten the kid safely away in some way if they’d tried.
Where exactly do you think they are going to get another gorilla? There aren’t many left. Personally, I think any gorilla’s life is worth far more than any child’s life simply based on their relative rarity. Kids are a dime a dozen. Gorillas, not.