Many years before tragedy struck the campus of Virginia Tech, Professor Librescu had faced the horrors of the Holocaust--and survived. So perhaps when he heard gunshots outside his classroom on the morning of April 16, 2007, memories of violence prompted him to block the classroom door. This gave his students time to jump from the second story windows. But the 76-year-old professor couldn't withstand the gunman's force and was shot to death. In the days following the attack, students were full of praise for Professor Librescu and his heroic action/act/behavior.

Which word should I pick in the above context, action, act, and behavior? And could you justify it with a few words? Thanks.
I think I would choose "act." "Action" implies movement-- to run away from this situation would have been an action. "Behavior" suggests something instinctive--to assume the fetal position when threatened might be a "behavior." Professor Librescu's brave choice was to stand between the attacker and the students, and that "act" probably saved a number of lives.
Thanks, Spides, for your justification.

I would pick "act" in that context, but strange enough, the original uses "actiion," which bewilders me very much.