Barack Obama, Robert Mueller, Boston Marathon bombing

Classic WhoWhatWhy: Was Tamerlan Tsarnaev a Double Agent Recruited by the FBI?

Last month, we reported startling new evidence that answered the questions, What did the FBI know about accused Boston Marathon bomber Tamerlan Tsarnaev — and when did it know it? Now the public is asking the same questions about Omar Mateen. For an in-depth look at how the FBI interacts with prospective informants, please see the story below. Published two years ago, it is still highly relevant.