Quite frankly, I'm surprised that more people in the U.S. military who are Muslims, Middle Eastern Muslims, don't go on rampages like this. The idea that this was something more than the product of frustration and potential mental imbalance is only tenable if you buy into the notion that there's a secret Muslim conspiracy at work seeking to disrupt American democracy. Which is about as likely as a secret Jewish conspiracy to control the world, which this sort of thinking resembles, as well as other likely candidates like Communism and Freemasonry. Despite all the hype, my guess is that this guy just extraordinarily pissed off about the situation in Iraq and channeled it through his religion, making him think that he was sort of some sort of terrorist ally. But there's quite a difference between yelling "Allahu Akbar!" and actually being connected with something like Al-Qaida, or more likely one of the more numerous terrorist groups operating in Iraq.
But then again, maybe there's a Muslim-Judaic-Bolshevik-Freemasonic conspiracy out there to control the world, with the Queen of England funding it all through drug sales.