One technique used by terrorist groups is to
1) claim they are responsible for an act when they really aren’t and
2) a group that is responsible will claim membership in a terrorist group, even though they have never had any previous contact with said group
Both give an appearance of terrorist groups being wide spread and well organized when, in fact, they may be neither
Do I know for sure about yesterday’s attack - No!! But if seems really unlikely that a vietnamese IBM ex-employee is connected to Pakistani terrorist.
It didn't seem very likely that a teen from Marin County California would be picked up on a battlefield in Afghanistan either. Or that a Puerto Rican from Chicago planned to set off a dirty bomb. There are plenty of Muslim converts in this country.