That's terrible :( I'm sorry for your loss.
I have to say though... 2 year old wandering by itself and opening doors, pulling out and dropping tubs, then replacing the tub where it was and you didn't notice the water bowl shifted or anything?
I agree you should also consider options that didn't involve your kid. Maybe its head wasn't crushed and the jaw just dislocated as it died or something. Maybe its head WAS crushed... maybe by the water bowl... MAYBE it wasn't the 2 year old that had the accident...
MAYBE there was a second shooter!