definitely not an open and shut case. the fbi is still trying to determine if the tsarnaev brothers are the only people responsible. that may take some time. bob is with me live. bob is a former cia operative and a cnn contribu so bob, how about that? you're not convinced the tsarnaev brothers pulled this off alone, are you? >> oh absolutely not, especially the last couple days it's come out the circuity on this bomb was complicated, wasn't taken off entirely from "inspire" magazine, wasn't downloaded from the internet. somebody was soldering and welding the stuff together who knew what they were doing. i doubt the two young men learned on their own. they were either shown by somebody else in the united states perhaps in dagestan. i haven't seen anything yet that would tell me. more and more we2% see this is a fairly complicated bomb and needed help. you and i can sit down and make one of these things and