Transcript for The NTSB Discusses Possible Causes of Deadly Train Derailment
We begin the news tonight with some answers about that train traveling at 82 miles per hour. What happened when the train hit the curve, the cars derailed and so many passengers were injured. There is new video tonight showing a closer look at the damage, the cars on their sides, the tracks mangled and destroyed and giant cranes lifted the cars upright. The black boxes on board now offering more clues to this story. Gio benitez goes in search of the answers. Reporter: Sources say human error is likely to blame for the train tragedy, investigators on the ground looking through the eery after math. Those tracks torn apart by a train traveling faster than it's supposed to. The speed limit in this area is 70 miles per hour. Once it reaches this curve, the speed limit drops down to 30. Tonight we know the train did not slow down. The train was traveling at as it went into a 30 mile per hour curve. When I heard about the speed, I gulped. It sort of takes your breath away. Reporter: The train lift for new york's grand central termin terminal on sunday making several stops without incident. As the train sped around the curve all 7 train cars derailed. Last this afternoon the ntsb announced the train's emergency brakes were fully activated five seconds before it careened off the tracks. I thought I'm going to die. Reporter: Passengers inside tossed around like rag dolls. By the time I looked up it was completely goo ly going off the track. Reporter: A photo obtained by abc affiliate shows people in overturned cars. Four people were killed. James ferrari, kisook ahn, donna smith and james lovell, a sound engineer from abc taking the early train to help stage the lighting of the rockefeller center christmas tree. He was just the best father i could ever ask for. Reporter: The train's operator, william rockefeller, seen here, is a long time engineer with a clean disciplinary record. Officials are interviewing him tonight hoping to build on what they have learned. This is raw data. It tells us what happened. It doesn't tell us why it happened. Reporter: Investigators have confiscated rockefeller's cell phone to find out if he was texting or talking before that crash. As you said he was a seasoned engineer for about 11 years on the job.
This transcript has been automatically generated and may not be 100% accurate.