seven people died in this tragedy. authorities have yet to release their identities. they say they are working to try and notify all next of kin first. and it's unclear if gildersleeve is one of them. his family saying they certainly hope he's not among the dead. >> erin what i'm trying to understand i think a lot of the people watching you buy a ticket for a train under your name, it's scanned when you get on board, how is it they don't know who was on the train, they don't know who's missing? >> reporter: authorities are pointing to several potential factors. first of all, the impact was so severe that it actually expanded the search area. they think it is possible some of these passengers could have been actually ejected from the train. they also say it's possible that someone who had a ticket for the train never actually boarded and they also say it's possible that someone could have simply walked away without notifying authorities. >> erin thank you very much. "outfront" tonight, beth