A biology professor accused of killing three colleagues and wounding three more in a shooting rampage at the University of Alabama in Huntsville on Friday was a suspect in the attempted mail bombing of a Harvard Medical School professor in 1993, a law enforcement official said yesterday. Bishop, 44, a professor at the University of Alabama in Huntsville since 2003, was arrested after allegedly opening fire during a faculty meeting Friday, killing three colleagues and wounding three others, reportedly after learning at the meeting that she was being denied tenure.