My Reaction: They know who has been bombing, so can't they find the people responsible?
According to the article, this is not the first bombing, but the latest one in a series. The article also says that the people responsible for the bombing are the Shia Islamist. The Radical Sunni military says that they will continue to follow the Shia Islamist movement's strongholds. They also have the help from the Iran military, so it's only a matter of time before the Shia are caught.