The United States was his home and wasn't; Pakistan, the land of his birth, was no longer home. It could no longer answer his needs.
He came to militant Islam after personal failure and disappointment. For him, the faith had become a weapon. He found it online, on the World Wide Web - that mix of modern technique and belligerent enmities.
Of all that has been said and written about this breed of "nowhere men" who have risen to war against the very messy world that forged them, the most poignant was said about the Lebanese-born terrorist, Ziad Jarrah, who is thought to have been at the controls of the plane forced down by its heroic passengers in Shanksville, Penn., on Sept. 11:
"He never missed a party in Beirut and never missed a prayer in Hamburg."
Jarrah had been the quintessential party boy in Lebanon, hip and trendy; he and his sisters were strangers to traditional Islam.
The pampered boy of an affluent family was unhinged by a radical reading of the faith that he found in the storefront mosques in Hamburg. Modernity failed and unsettled Jarrah.
There are echoes of Jarrah's story in reports about the older Tsarnaev brother, Tamerlan.
Like Jarrah, Tamerlan was in his mid-20s. He had become a legal U.S. resident in 2007; he had shown no early interest in Islam. His passion was boxing.
But then Islam entered his life through the social media. Investigators found explosives and a trigger on his body after his death in a police chase.
Civilizational battles were once waged by warriors who donned the garments of different lands and spoke the languages of different worlds - the Moors on one side, the Castilians on the other. The borders were easy to see and to make out.
The global landscape is different today. It is boys with baseball caps who carry death and ruin in their backpacks.
Home is neither in the lands of their birth nor in the diaspora communities where people flee the fire and the failure of tormented places.
No "intel" can find and identify this unsettled breed - ordinary neighborhood types who step forth to do battle against a modernity, and an order, they had once yearned for.
Fouad Ajamiis a senior fellow at the Stanford University's Hoover Institution and author of "The Syrian Rebellion."