He had a house full of guns, semi-automatic rifles and hundreds of rounds of ammo at disposal. If you don't see any problem with that, then nothing more to add I guess.
Who said that I don't have a problem with civilians having weapons... That wasn't my point and obviously you can read that in my previous comments. I DO indeed have an issue with civilians carrying weapons, but here in America it will be impossible to control such things. "Rednecks" will always advocate for availability of weapons for all their hunting escapades and whatever, just feeling more "manly" having a weapon on them for self-defense, while many other people are paranoid and will buy weapons for their protection. These people will always have a case to make for lawmakers. And for the hundredth time, no matter how strict gun laws get, a nutcase like that shooter will end up getting a gun somewhere, trust me.
We understand very little of the human brain and how it works to say that we will be able to make any substantial progress towards detecting and controlling mental illnesses in your and my lifetime(and in the next 100 years). Unless nature endows us with a genetic mutation which turns 10% of earth's population into psychic beings capable of detecting criminal thoughts before the crime occurs (cue Minority Report), we are many generations away from being able to prevent such crimes through psychological evaluation of said future criminals.
It is true that we will never be able to perfectly control the distribution and use of firearms even if effective controls were imposed on society at large, but the data (shown below) shows that there enough correlation between strict control of firearms and homicides and other firearm related deaths, to impose such regulations. No regulation is perfect, but the goal here is not perfection, but minimization of firearm related homicides/suicides.
Firearm-related death-rate per 100,000 population in one year
More than half that number is related to suicides I see, but regardless the way I see it. Stricter gun control will lower those situations that usually involve 1 person shooting another person, but such shootings like yesterday will most likely continue to happen in my opinion regardless of the gun laws.
Obviously mental behavior and health is a very difficult field to study and analyze, and there is only so much people can do as it isn't as obvious as a broken leg, but if schools and the government can provide more information on such things and make the public better aware of such a misunderstood topic, people would be more inclined to bring someone like the shooter into some clinic to be properly taken care of.