Guys, guns are fantastically simple machines that have been around for centuries. No amount of legislation is going to make them vanish or uninvent them. Somewhere between 1/3 and 1/2 of the households in this country have a gun inside. About any idiot with free time can craft one.
You can pass the most draconian gun laws in the world, and that's not going to make guns disappear, uninvent them, or stop maniacs from doing maniacal things. In fact, the places with the strictest gun laws have the highest murder rates.
The guns this guy used were already illegal, just like murder is already illegal. What do want to do, make them super-illegal?
Half of you nitwits lose your civil rights 4th amendment crap over police detaining people for 5 minutes to check for warrants and citizenship, and start uncontrollably blurting "racism" and "profiling". Yet you want crap on the 2nd amendment and have people to pay what is essentially a poll tax and pass a rigorous background check (administered by who?) to buy a gun that tens of millions of people already own. We have guns laws, lots of them, the ignorance exhibited on that topic is insane.
If you to solve this problem you need to start thinking outside of the box. Because legislation has proven it won't stop criminals from doing criminal things.