However , that teacher , Dave Sanders , proved another hero , having helped many students to safety before losing his own life .
Best known is the Columbine High School massacre in 1999 , when two students killed 12 students and a teacher .
That teacher , Dave Sanders , proved another hero , having helped many students to safety before losing his own life .
Best known is the Columbine High School massacre in 1999 , when two students killed 12 students and a teacher .