You need to look around and find the full video. For some reason, most of the videos EDIT OUT THE FOOTAGE OF THE KID BEING DRAGGED not once but two times! Like a rag doll. You can see the gorilla is agitated, curious and really treating the kid like a toy. If it was my kid I would have shot it dead myself and danced on its grave.
The zoo is the responsible party, it had a makeshift wooden fence with rungs spaced far apart that allowed the kid to slip through.
You need to look around and find the full video.