You understand that your own argument applies here too, right? He wasn't convicted of any felony, thus could purchase a gun. He wasn't committed to any institution, thus could purchase a gun. What changes to our background check process do you propose that would stop a guy who had no felonies on his record and was not institutionalized or put on a "unstable" list of some kind that would have prevented this?
Would a waiting period have stopped it?
You tell me. Probably not. People who do these kinds of shootings don't usually do them on a whim (always exceptions I suppose). You don't honestly think that someone who's obsessed with the idea of going out in a blaze of glory and taking as many of his co-workers with him is going to be deterred because he'll have to wait 15 days to do it? It's kind of a "once a lifetime" thing to do, right?
But the number of contractors who own guns does not overlap 100% with the number of mass murders by contractors, does it? That's a silly correlation. There's also a 100% overlap between mass murders by contractors and mass murders by contractors who ate food in the previous few days. So clearly we should ban food! Yeah. Dumb logic Smash.
I was going to explain this and how Hannah spotted the problem with your post, but I decided it would be better to see if you could catch up to an 8 year old. Good luck.
Given that it's the exact same problem with the logic in your post, perhaps you should ask yourself why you failed to spot something an 8 year old could see was wrong. You get that the logical structure I just wrote is exactly identical to the one you did, right? Or do you not?