Frankenstein - ch. 11-12

Now the creature begins telling his story. I find it interesting that the story begins with Walton telling this whole story to his story about Frankenstein telling his story to Walton now about the creature telling his story to Frankenstein. That is a frame story if I have ever seen one. The creature tells his story about his travels and how he scared everyone he ran into. The story that amused me the most was the one about the shepherd who upon seeing the creature, "ran across the fields with a speed of which his debilitated form hardly appeared capable." Then the story gets plain creepy. The creature observed every action of the family consisting of the blind father, Agatha, and Felix. As a sort of thanks for his observing them, the creature helps the family by bringing them fire wood or clearing a path of snow. The creature wants to learn to speak in order to communicate with the family. The creature is surprisingly intelligent and finds a way to vocalize some words. Obviously, the creature found some sort of way of learning to speak intelligently as shown in his conversation with Victor. The creature claims that he has a gentle demeanor and he planned to use this to win over the family. If the creature has a gentle demeanor, then why did he kill William?