BlackFive

This guy is still tough on himself for not acting sooner.  A real hero who did what had to be done.

"It bugs me that he got another round off"

And as our own Grim says, if he had cowered and not taken action, might have been killed, too.

Mr. David Benke stopped a school shooter 'with the faith of his body,' as they used to say: wagering his life against a killer, and saving many others in the process. He also came away unhurt himself, whereas had everyone cowered he could well have been shot. 

Another teacher also helped subdue the shooter.