With today's sentencing of T.J. Lane, look back at other major school shootings in U.S. history.
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Sept. 29, 2006: Christopher Williams, 27, went to Essex Elementary School in Essex, Vt., looking for his ex-girlfriend, a teacher. He couldn’t find her, but fatally shot one teacher and wounded another. Williams also killed his ex-girlfriend’s mother. He shot himself twice in the head after the rampage and was arrested.