For years, the F.B.I. has been closely watching the Shabab, the Somali Islamist group that has claimed responsibility for the Nairobi massacre and recruited numerous Americans to fight and die — sometimes as suicide bombers — for its cause.
The Shabab has already attacked most of the major actors trying to end the chaos in Somalia — the United Nations, Uganda, aid groups, the Somali government and now Kenya. The United States has spent hundreds of millions of dollars bankrolling anti-Shabab operations for years, and there is growing fear that the group could turn its sights on American interests more directly, one of the reasons the Obama administration is committing so many resources to the investigation in Kenya.
Source: NY Times