PHOENIX – A 27-year-old man has pleaded not guilty in the fatal stabbing of his 12-year-old half-brother.Andrew Ward entered his plea Thursday morning. He is charged with first-degree murder, child abuse and aggravated assault. Ward was arrested March 12 after calling 911 from a convenience store near his family's Phoenix home and said he had stabbed someone.Police went to the home and found Austin Tapia with multiple stab wounds. He was pronounced dead at the scene. Police said the brothers were home alone while their mother and two sisters were out to dinner."When asked why he did this he said, 'Honestly I just felt like killing,'" Phoenix police Sgt. Steve Martos said.