I saw the video of this shootout. Pretty determined BG. Interesting report.
I like the comment left by Ignatius28 -
"....The only gun that I have truly seen demonstrate true one shot stoping power is a 12 guage shotgun, and some rifle bullets....."
Though I'm not sure how effective a 12ga would have been in this situation, I could easily subscribe to the idea that a 12ga with the right shells, CBM, would be a "one shot stopper" in most HD situations.