Would have, without question. The available videos show it clearly.
The dumb beast has no judgment of the consequences of dragging a human child around the way it was happening.
Insofar as "dumb" means "unable to speak", I think we can accept this statement, keeping in mind that the consequences of the action you mention were evidently nil.
It's a fascinating idea, the mind of a gorilla, because it seems evident that he is indeed possesed of mind, akin to us, but yet alien to us. We can recognize it, but we cannot comprehend it. Surely in this case, his mind was filled with confusion and uncertainty. I have no doubt his mood could turn on a dime in those circumstances, and it's impossible to second guess the actions of the authorities in putting down this gorilla, but even so I would count his death as a tragedy.