Speculation rises on days like these about the role of God in human affairs, but for my part I accepted as adequate the concept of free will a long time ago. I believe God gives us the power to choose good or evil in everything we do, and flawed as we are, through action and inaction, consciously and unconsciously, we frequently choose evil. A few among us choose to perpetuate evil of a magnitude that we consider their actions to be crimes against humanity. The September 11th hijackers made such a choice and were such men. To my way of thinking, God had nothing to do with their actions other than to lay open to them the same power He gives us all.
Whether heaven holds a place for the unspeakably evil, I don’t know. Given that we can barely comprehend the infinity of God in this existence, divine justice in the afterlife seems speculative. But if heaven exists, surely it exists for the victims of atrocities like 9/11/01.