EDIT: I see my post is being downvoted. I know that it may come across as insensitive to immediately leap to the gun control debate, but frankly I'm more angry than upset by this news. How many times does it have to happen? We have a good 48 hours of emotional outpouring and then everyone forgets it ever happened.
How many times are we going to find out someone had a history of mental issues and nothing was done? How many people are reluctant to take proper medication because they view the effects of the medication worse than what it trying to treat. We have a lot of people coming back with PTSD, we need to get better at this.
I remember OK and that was farm products (which some companies still sell at automated machines). IEDs, pipe bombs, propane canisters, Molotov cocktails are all capable of killing a lot people and are easier to build or acquire than guns.
But mental illness itself has no check point. How can we ensure that people do not have untreated Schizophrenia? Mandatory checks for everyone once a year? I'm really not sure how it could be done.
Do all of that, and anyone who tries to buy a gun without a license can safely be assumed to be up to no good. You don't even need to license firearms themselves, which is unpopular.. just the owner themselves.
Most of these nutters are buying their guns legally. Hell, I bet a lot of them buy their guns not even fully realizing what they will eventually do with them.
Illegal sale/ownership of guns is just an issue for the police to handle. I don't think there is much progress to be made on that front.