I just ran through the "Active Shooter Preparedness" online course on the DHS website. It goes into much more depth about before/after stuff, but the basic advice for "during" is still (1) evacuate if you can, (2) hide if you can't, (3) fight back as a last resort if your life is in imminent danger.
Despite a great deal of attention paid to how to prepare for the possibility of such an event: know where the exits are even if you're a visitor, etc. -- NO mention was made of considering, ahead of time, what objects in the immediate area might serve as weapons of opportunity.
I'd conclude from this that the folks who put this together don't really see fighting back as a real possibility, nor do they want to encourage it.