I was robbed at gun and knifepoint by two Jamaican gang members in New York City. One had a 1911 to my abdomen. The other was behind me with a rusty knife drawn back ready to stab. Just before the robbery there was a moment when the robbers gun was exposed in his waistband and I could have easily killed him, had I been armed with more than a knife.
I read what happened to Bob Lonsberry. All I can say is that it gets easier to shift to full aggressor mode when confronted by a criminal with experience and training. If a criminal accosted me and announced a demand for money today I'd blow his spine out without hesitation. No effort to walk away or to turn my back to him. No question about it. Read Lonsberry's story. He was fully prepared to let that animal kill him.