rescue came from these interviews by the fbi and at the time they also thought that if they carried out this rescue they might also be able to nab emwazi which is something we did not know. >> what about this other presumed westerner who was featured in that isis video purportedly showing the beheadings the execution of those 21 egyptian christians in libya? i assume u.s. officials, others are trying to track him? he spoke seemingly with almost an american accent. >> reporter: right. exactly. that's exactly what alarmed the fbi. they have opened an investigation now because they want to know whether or not, again, the operating assumption that they have is that this accent appears to be western. they think that perhaps that person might have spent time in north america, just again, listening to the accent. they don't know for sure whether that person spent any time here in the united states but this is something that they are now digging into and they are hoping