DID AMTRAK'S ENGINEER CAUSE THE DERAILMENT?

In what Philadelphia Mayor Michael Nutter called a "disastrous mess" and something he has never seen in his life, investigators are already - preliminarily - looking at Amtrak's Engineer as one possible cause of the derailment. Investigators say the Engineer may have driven the train t106 mph around a curve listed with a maximum speed of 50 mph. The families of the deceased and the injured will want to know:

How did Amtrak allow this to happen?

Did Amtrak have prior knowledge about this Engineer?

Is this the most severe curve in the area and if so why did Amtrak not install equipment like Positive Train Control (PTC) on this section of track?