Duck and cover or run is about the only strategy that would work in this incident. Especially since most CCW-ers load hollow points, rather than FMJ, and hollow points are quite easily stopped by body armor.
The thing that the shooter did not know, since he got all his info by speaking with gun dealers, who are willing to say anything to sell you anything, is that the AR-15 package jams easily when fired a lot. So fortunately his rifle jammed on him, and he did not know how to unjam it. This saved a lot of people, since most of his ammo was 5.56 rather than shotgun or 40 cal.
Had the shooter known what he was doing he would have brought a different weapon than the AR. Good thing he did not.
Thoughts and prayers go out to the victims and their families, and the community there.