He was a law abiding gun owner up until he went and killed a bunch of people
Well, only for a little over a week, but an excellent point nonetheless.
There is no "Pre-Crime", people cannot be convicted, or denied rights, based on what they "might do". The FBI interview came up with nothing, the guy passed the background checks. This is as it should be, he was an American citizen, he had committed no crimes that disqualified him from owning a firearm { since apparently his spousal abuse wasn't documented } he was therefore able to legally purchase a firearm.
The fact that he had become an radical Islamic sympathizer, while disgusting, isn't illegal. We're going to be hearing tons of speculation about how to "prevent" this kind of thing from happening, but the fact is, in a free society you can't. Not without restricting or removing rights for everyone, which we are going to hear those on the left, and even many on the right screaming for at the top of their lungs.
The problem is, we're missing the point. The argument shouldn't be framed in terms of gun control, it should be framed in terms of terrorist control. The Islamic ideology { I refuse to call it a religion } is utterly incompatible with western society. It always has been, it always will be. Regardless of how many people call it "the religion of peace" it's quite obvious that it's not. It's an ideology of conquest, unless and until all other religions or ideologies are destroyed, and everyone that practiced them is either converted or killed, they will never stop. This is what they believe, it's written in their book, even the supposed "peaceful" Muslims believe this. That is why they will never assimilate and become part of any society they enter, their ideology doesn't allow it. They are, for lack of a better analogy, like the Borg.
We're going to be seeing more and more of this kind of violence. Until we face the truth about Islam and deal with the reality of the enemy among us.