Emergency personnel work at the scene of a deadly train derailment, May 13, 2015, in Philadelphia.

Rescue crews and investigators inspect the site of an Amtrak train derailment in Philadelphia, May 13, 2015.

Emergency personnel work at the scene of a deadly train derailment, May 13, 2015, in Philadelphia.

Emergency personnel walk near the scene of a deadly train wreck, May 13, 2015, in Philadelphia.

Emergency personnel help a passenger at the scene of a train wreck, May 12, 2015, in Philadelphia.

Emergency personnel work the scene of a train wreck, May 12, 2015, in Philadelphia.

A crime scene investigator looks inside a train car after a train wreck, May 12, 2015, in Philadelphia.

Emergency personnel work the scene of a train wreck, May 12, 2015, in Philadelphia.

Emergency personnel work the scene of a train wreck, May 12, 2015, in Philadelphia.

A crime scene investigator looks inside a train car after a train wreck, May 12, 2015, in Philadelphia.

Emergency personnel work the scene of a train wreck, May 12, 2015, in Philadelphia.

Emergency personnel work the scene of a deadly train wreck, early on May 13, 2015, in Philadelphia.

Emergency personnel work the scene of a train wreck, May 12, 2015, in Philadelphia.

Emergency personnel work the scene of a train wreck, May 12, 2015, in Philadelphia.

An Amtrak train crashed on May 12, 2015, in Philadelphia. Train 188 was traveling from Washington to New York City.

A passenger is carried following an Amtrak train crash on May 12, 2015, in Philadelphia.

Passengers from an Amtrak train that crashed gather on May 12, 2015, in Philadelphia.

Emergency personnel transport a person at the scene of a train wreck, May 12, 2015, in Philadelphia.