Holey Hannah, an astounding amount of incivility and irrelevant partisanship going on here.
There is really nothing much to say about this incident, other than "well, that's a shame... glad it didn't happen in my town," and move on... which is what most Americans did when they encountered this story.
The main reason for that is: there's not much to be done about this sort of thing. In a nation of over 315 million, with the particular social and economic problems and ethnic issues and etc that we have, things like this happen now and then.
Our mental healthcare system took a blow in major budget cuts in the 80s, particularly mental hospitals for the criminally insane and the dangerously disordered. As a result, a lot of people ended up on the street who needed to be housed in a secure unit. In part, this sort of thing is where we reap what we've sown in terms of national mental health.
OTOH, the long-term trends for violent crime and murder have been substantially DOWN for about 40 years now... so it really isn't as big an issue as the dramatic and overhyped media coverage make it seem.
As for guns, well... there are arguably more guns in the country than people, most of them never registered, and no action short of draconian police-state tactics is going to make them go away. There's little point in attacking it from that end.
So, frankly Paul, we shrug and we're thankful it wasn't anyone we knew and we go on with our lives... just like people who live in heavy tornado alleys like the Texas panhandle and Oklahoma after a storm; just like Hawaiians after an eruption; just like people continue to drive on the highways despite 40,000 traffic fatalities a year, just like we don't talk about restricting alcohol even though it is involved in roughly half of all fatal accidents and murders.
There's not much can practically be done about it so we shrug and carry on.