It was a targeted killing with an unknown motive as of yet, one in which the killer and victims knew each other. The killer had a prior criminal record including violent crimes. While you may argue that anyone who kills someone else in a non-self-defense situation fits the definition of "mad", this does seem to be different from the "madman with a gun" scenario originally hypothesized.
FWIW, in a nutshell, I posted that post because I too felt it was a sad and tragic event which William brought to our attention. Second, I didn't call the event a domestic violence act, the media did and that is why I provided the links in the post. More importantly, Mark being the framer of the thread, we need to ask him if domestic violence is a component to his questions. Lastly, am really not sure if it is important to discuss how domestic violence does or doesn't fit. The question is asking how we plan or prepare for a "very rare" occurring act of violence by a "madman with a gun."
With that in mind, I figured domestic violence wasn't part of the questions because his original post states, "...for that very rare occurrence of a madman with a gun?" And the quote from the article by Lott, dealing with gun laws that Mark used. Domestic violence happens more frequently that say a "madman with a gun" like the horrific sniping done by Brenda Ann Spencer killing elementary children and two adults. This such event is what I understood the original post's questions to be. But I will welcome any changes to that by Mark, as he is the original framer of the questions.