2nd amendment says citizens can bear nuclear arms.
I have a few friends who own more firearms and ammunition than this killer. If they could buy heavier stuff they'd mortgage their homes to have it. They want bigger toys like grenades. They want those M16 grenade launchers and different rounds. They want mortars and howitzers and machine guns. There's no limit except maybe cost as to what they would like to obtain.
Admittedly, none of these guys are like this killer. Most have never even fired their assault rifles, having them is satisfaction enough, and I suppose if they obtained nukes they'd hold them the same way.
What I need to do is find out the background of why the U.S outlawed the sale and possession of machine guns for Joe Snuffy back in the 1930's. Maybe it was because of organized crime activity. But the second amendment only says arms, not prohibiting machine guns or light anti-tank weapons. So 2nd amendment worshippers should have anything they can afford to purchase, constitutionally speaking.