Before you read the first chapter you must know that Peter doesn't need the full moon to turn into a werewolf he is the size of a bear slightly bigger. But on the full moon when he changes it is into an actual wolf in size and mind. When a werewolf kills a human it tears at their mind the more humans they kill the more they go insane. Killing a human is breaking one on of the most sacred pack laws as werewolves are meant to protect humans not harm them.