It looks very much like the shooting of four Marines at the Navy Marine Corps Reserve Center in Chattanooga, Tennessee on July 16 was motivated by radical Islam. The shooter, Mohammod Yousef Abdulazeez, reportedly posted on his short-lived blog on Islam two posts referring to preparing for death through Islam. He praised the Sahaba (the followers of Muhammed) for waging jihad. (The blog has since been taken down.)
A Tweet associated with ISIS appeared to some to point to a connection with the Syrian/Iraqi jihadist army, and several news outlets ran with the connection before it became evident that the Tweet had actually been posted three hours after the shooting. There is presently no evidence of any direct link between Abulazeez and ISIS. Undoubtedly, ISIS would love to claim credit; they are very, very good at information operations. It would only build their legend further.
But that is the nature of modern, open-source warfare. There might be a connection, there might not. Converging methods and interests. It may be discovered (though it will probably always be a matter of guesswork, as Abdulazeez is dead) that he was, in fact, inspired to conduct the attack by way of ISIS propaganda. But there doesn’t have to be a direct chain of command, and there probably isn’t. All that is needed is motivation and means. And the reality of modern globalization means that there is no shortage of motivation.
There are those who are saying that this is another reason why ISIS has to be destroyed. I’m not objecting to the head-choppers getting slaughtered wholesale. But it won’t end the problem. It’s far, far too late for that.