No one has ever said that concealed handguns could stop all crime. So if the author is arguing that concealed guns can't stop all crime, he's just demolishing a straw man. The advocates of concealed carry merely say that, on balance, these laws reduced pain & suffering among good people by sowing FUD among violent criminals.
I'm sorry the experience was so traumatic for the security guard. Hopefully time will help soften bad feelings. I'm glad she's still alive -- and I'm glad the perp won't be hurting anyone else.
When a person has beaten you half to death and is still in the immediate vicinity, they are still a threat. I don't think there is a jury in America that would convict this woman.
Last I read, she was being charged with murder. Her ordeal has just begun, sadly.