The 16-year-old high schooler arrested Sunday for allegedly killing a classmate in Nagasaki Prefecture says she cut up the body of her victim because she was "interested in trying dissection on a human after dissecting a cat and reading medical books," a police source said.

Much as her remark may cause horror, in hindsight there appear to have been warning signs in the girl's life, and her teachers and others who knew her are reflecting hard about how they should have reacted.

The girl allegedly killed her 15-year-old classmate at a condominium where she was living by herself in Sasebo, a port city with a population of around 255,000.