That's true.
The guy shot 2 people and left. So if YOU were at the cash register, armed, exactly what would you have done? Shot the perp in the back? In his truck?
Yes, I'd have dropped him, either in the front or the back or the side, whichever shot presented itself. If someone commits a shooting, an axing or a knifing and leaves with the weapon, the legal presumption is that he is on his way to commit another murder, and you are allowed to shoot him. It's a very clear exception to the "can't shoot a felon who's leaving" rule. These psychos often have a little list in their head. "After Lowe's, my old job. Then Mom's. Then the ex-wife."
This kind of thing happens all the time, and will continue to happen regardless of CCW in any State. I think the stats show it happens a lot less in states with CCW, that there is a clear dropoff in incidence. These guys are out to settle a score, and not get dropped in their tracks, (at least not before completing their "mission.")
Not in Wisconsin. Not in Texas, according to a prior post.
And, given the mindset of both journalists and DA's in almost the entire USofA, noplace else, either.
That "exception" you cite most likely applies only to LEO's, after they've screamed "stop/drop" a few dozen times.
But hey--try it sometime. Let me know how your case turns out.