and provide technical expertise to help us resolve and figure out what was the particular damage pattern on one of the windshield. but we are investigating it at this point. and we've just asked them to come in and help us out on identifying that fracture pattern. >> tom costello is outside the 30th street station in philadelphia. tom, it does seem as if ntsb is trying to tap the brakes on this growing story that maybe some outside sbitd or force caused this accident. >> reporter: here's why they are concerned about this. they had a septa regional train hit by something. the engineer thought he had been shot ought. we had another train hit by something, a brick or something. and potentially in amtrak train 188 hit by something potentially on the windshield. nobody knows the answer to this right now because the engineer says he doesn't remember. but the question is is it possible that when that brick or whatever it was hit the front of am track 188 if that's in fact what happened that it rattled this engineer that he lost