A special needs student was killed Tuesday, after she was hit by a MAX DART  trolley.  Police say the young woman, a student at the Horizons School, was crossing 20th Street South when the vehicle hit her, as it turned  from 14th Avenue South.  The victim was not immediately identified.   Witnesses said the victim was dragged a short distance before the trolley stopped.  A doctor and others ran over to offer assistance, but were unable to save the woman.