The Independent reports that the boy crawled through the railing and then fell 12ft.
400lbs - woo that's one big boy. 17 year old Harambe. Endangered species too..
Zoo even said it didn't appear to be attacking the boy but they shot it regardless. Didn't tranquilise it as it's not immediately effective, thus making it a more dangerous situation. Fair enough.
Guess they did the right thing after all. We've all seen the lion and tiger videos