While federal investigators had tracked the movements of American recruits to the Shabaab since at least early 2008, the F.B.I.’s case did not swing into high gear until after Shirwa Ahmed’s suicide attack that fall
“Why are we sitting around in America, doing nothing for our people?” one of the men, Mohamoud Hassan, a skinny 23-year-old engineering major, pressed his friends.
In November, Mr. Hassan and two other students dropped out of college and left for Somalia, the homeland they barely knew. Word soon spread that they had joined the Shabaab, a militant Islamist group aligned with Al Qaeda that is fighting to overthrow the fragile Somali government.
The students are among more than 20 young Americans who are the focus of what may be the most significant domestic terrorism investigation since Sept. 11. One of the men, Shirwa Ahmed, blew himself up in Somalia in October, becoming the first known American suicide bomber. The director of the Federal Bureau of Investigation, Robert M. Mueller, has said Mr. Ahmed was “radicalized in his hometown in Minnesota.” (read full story)