traffic cameras at individuals' houses, trying to find a common link. >> how do they think this could have happened? >> they say you can set this up so it doesn't go off until someone trips it. these people know what they're doing. and now we need to find out who has the capability of making, setting up this bomb and tripping this device. >> the fbi wants to speak to the bomber. what are the chances the bomber would get in touch with the fbi? >> it's hard to say. they could do that but everything has been pretty quiet. it was ten days before the