BEIRUT, Nov 21 (Reuters) - An American woman missionary was found shot dead in southern Lebanon in the infirmary where she worked, a security offical said on Thursday. "The missionary, she was killed. She was hit by shooting," the official said. "They are investigating it." The official said the woman was 30 years old. She was shot when she entered the clinic in the southern port city of Sidon. He said no motive was known for the shooting.