I'm just going to say what needs to be said, no matter how ugly.
I don't know why Sulejman Talovic did what he did, maybe his girlfriend cheated on him. But the most obvious probable cause was his faith. It has been confirmed that Talovic is Muslim. It would be intellectually dishonest to say Muslims and Christians are equally prone to radicalization in today's world. It's a fact that Islam is more easily subject to radicalization today, and it shouldn't need to be repeated after 9/11.
With the war on terror, constant Israeli-Palestinian conflicts, the war in Iraq, threats from Iran, and increasing jihadification of Muslims, the Sulejaman Talovics of America are inevitably on the rise. Soldiers fight abroad and police can only do so much, the citizens of America are the front lines.
"The great object is, that every man be armed."
It's been over two hundred years and our founding principles still remain guardians of freedom and survival. Those were Patrick Henry's words from 1788.