some of them severely when the commuter train entered a sharp turn going 82 miles an hour in a 30-mile-per-hour zone. nic robson is at the crash site with the latest. >> reporter: human error, william billy rockefeller's daze, increasingly the probable cause. his union representative saying he was nodding off and caught himself too late. >> he is extremely distraught over it. and he feel for the families. i don't believe that in my opinion, anybody could ever make billy feel worse than he is making himself feel today. so billy feel terrible. whether it was his fault or not his fault. >> having eliminated a number of possible causes including signal failure, the focus of the investigation increasingly falling upon william rockefeller jr., the train's engineer. >> the operations group