Can't say what I would have done if I had been on that board, but if given a clear shot I have practiced to take it. I will never know for sure until put in that position for sure, but the reason I learn, train and practice is to be ready to take the shot.
If you are going to wait till he shoots first you may just find out how hard it is to pull a trigger with a third nostril!
If my emotions were in check I would have done all I could have to put this coward down!
The only thing worse than committing suicide is forcing some one to do it for you.
Look at it from this perspective.
Say the Board President, who appeared to be the primary target, was a loved one, spouse, child or sibling.
I don't think many would wait until that first shot was fired and the loved one lay bleeding before taking action to put the guy down.
I don't think i could pass on the chance to avoid the possible death of an innocent just because the innocent was not close to me.