Another student was wounded in Tuesday's attack, and the assailant -- also a student -- was shot and killed by a police officer stationed at the high school in southern Maryland.
The girl, 16-year-old Jaelynn Willey, was shot in the head by the attacker, with whom she had had a relationship.
Her parents told a news conference Thursday night that their daughter was brain dead.
The Great Mills High School shooting came about five weeks after a massacre at a Florida high school left 14 students and three adult staff members dead and sparked a grassroots campaign for tougher laws on gun ownership.
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