Shame people are now prohibited from protecting themselves...
FEMA EMI offers a free version such instructions in their IS-907 online course, Active Shooter: What You Can Do. The advice is simple, clearly laid out, and free.
The Center for Personal Protection and Safety (CPPS) offers for sale a DVD called Shots Fired: When Lightning Strikes (which correctly summarizes the frequency of such incidents).
I have no issue with shall issue laws or the idea of lawfully armed private citizens carrying concealed almost anywhere, but active shooter situations are rare; situations where lawfully armed citizens have intervened to stop one even more so.