How do you think the goblin rat was killed in "The Boy Who Drew Cats"?

Because of the nature of the Japanese fairy tale "The Boy Who Drew Cats," there are a number of variations on the story. Many of them change the origin or name of the main character or the descriptions that occur after the "goblin rat" is killed. However, they all follow similar patterns, and the death of the giant rat always occurs for the same reason.The main character is a young boy who is obsessed with drawing cats. Because of his obsession, he isn't of any use at home, so he is sent away to become a priest. However, rather than study and train, he only wants to draw cats on the walls of the temple in his free time. This is frowned upon, for obvious reasons, and so he is sent away to another temple. The second temple he goes to appears to be abandoned and is also lined with clean white walls. The young boy is ecstatic and immediately (as you might have guessed) begins to draw cats all over the place. In some versions of the story, he eventually draws a cat bigger than all the others; in other versions, he just draws a lot of smaller cats. He eventually tires and goes to sleep.He is awakened in the middle of the night by a loud crashing and the sounds of a fight. He stays quiet, and the fight continues for a long time. Eventually it ends, and when he goes to investigate (the next morning, in most versions), he finds a dead giant rat. As he looks around, he then notices that something has changed about the cat(s) he drew.
In the stories involving one enormous cat, often the cat is facing the direction opposite of that which he had drawn it. In the stories that involved him drawing several smaller cats, the giant rat is often bloody, and the drawings of the cats all have blood in their mouths. No matter the variation though, it is clear that the child's drawings came to life during the night to protect him from the giant rat, and they eventually killed it after a long struggle. The young boy vows to never stop drawing cats from then on.