This is all scrambled. The suspects were picked up by police, not townspeople, and they came under suspicion because they were talking in dialect and no one could understand what they were saying. In the charged atmosphere after Ayatollah Hakim's death, the nearest foreigners were grabbed as suspects. They have since been released, and the investigation into his death is quite murky.
The town in which all this took place, Najaf, is one of the religious centres in Iraq. Despite the fact that it is peaceful, and has been accepting of the new order, obviously the very fact that it is an Islamic shrine town will be enough eventually to put it in the firing line.