Mary Knowlton arrived at the Punta Gorda, Florida, police station yesterday to learn how to be a community steward. The 73-year-old was there as a student in the citizen police academy, a two-hour course intended to give an intimate look at what makes the department in the quaint Florida town work. These scenarios are usually safe, acted out with either fake or empty weapons. But when the officer's gun was fired, Knowlton - a mother, wife and career librarian - was hit with live ammunition.