Unable to confirm the account of the nearby septa train which had been hit by an unknown projectile. the ntsb listened to all traffic from the area that night. authorities say they are still looking into the possibility. >> at this point, we really want to chase this lead down. we heard from the assistant conductor that is what she believes she heard about the conversation about that. we now see a mark on the windshield that we want to look at. so we will look at everything. >> reporter: today, fbi forensic investigators are expected to examine the fist-sized circular marking on the left side ...