year-old boy stabbed his sister to death early Thursday morning shortly after being released from the mental hospital to which he had been taken the night before when he first attacked her, police said. The boy attacked his 16-year-old sister Wednesday night and was taken to the police department, which referred him to the Jizan Mental Hospital. The hospital treated him with tranquilizers and handed him over to his father. When the father went to bed, the boy took a kitchen knife and attacked his sister again stabbing her in the heart, chest, breast, and left hand, said Col. Owad Al-Qahtani, spokesman of the Jizan Police Department. The father was awakened by his daughter's screams for help, but it was too late. The single-parent family had another son who was not at home when the incident occurred. The girl was rushed to the hospital but was pronounced dead upon arrival. The boy was arrested and taken to the mental hospital again.