At least six people have been killed and dozens wounded after an Amtrak train bound for New York City derailed in Philadelphia. Eight people remain in critical condition, and not everyone on board has been accounted for. The train had departed from Washington, D.C., carrying more than 240 people. Six cars overturned, with sections of the train so mangled people had to be rescued with the aid of hydraulic tools. Philadelphia Mayor Michael Nutter called it “an absolute disastrous mess,” saying “I have never seen anything like this in my life.” The cause remains unknown.