Theresa Miller, 44, a Columbine High School teacher who ran through the hallways warning people during the 1999 massacre there, died Monday of colon cancer in Littleton, Colo.

The diagnosis came a few months after two students attacked the school on April 20, 1999, setting off explosives and killing 12 students and a teacher before killing themselves.

Ms. Miller extinguished a fire started by a pipe bomb, led students to safety and stayed with fellow teacher Dave Sanders as he died from gunshot wounds. The next day, President Clinton noted her heroism in an address to the nation.