He may very well be a victim who was bullied by someone in society, or even society at large. If so, that's where we can look internally for ways to prevent that from happening, but the sad fact is that no one can be protected from life, and some people are going to get the short end of the stick now and again. Ailene Wuoronos comes to mind. She was crapped on by life at every opportunity, but it doesn't dismiss what she did. Best we can do is show empathy and sympathy, but it doesn't excuse this shooter's behavior in any way. We're long past trying to find out why in these instances, because they are the irrational acts of irrational minds, and it cannot be rationalized.
As far as limited blade length, caliber, whatever, yes, that's true. No one ever said the Constitution isn't being trounced on all the time. "Shall not be infringed" is plain, direct and unambiguous, yet it gets infringed with every law regarding guns and other arms.
People think that if we didn't allow automatic or semiautomatic weapons with large magazines of ammunition that things like this would not happen. They're wrong in their thinking. If someone wants to do a lot of damage and injure or kill a lot of people, they will figure out a way to do that. They did it before automatic weapons were invented, and they can do it if they are outlawed. Don't kid yourself into thinking otherwise. Do you know how many people were killed in Oklahoma City, without a shot being fired? 168. The Beirut Barracks attack, 299. The 911 attacks, 2998. Not a single person died from gunshot wounds in any of these attacks. In the theater, instead of a couple of smoke bombs and tear gas and gunfire, it could have just as easily been half a dozen homemade hand grenades that killed and inured even more than the gunfire did. He could have parked a truck loaded with diesel fuel and fertilizer out back against the building and taken nearly everybody out, automatic rifle not required.