Train derailment investigation

Paul Nussbaum and Jonathan Lai have an article in The Philadelphia Inquirer about the derailed train:

A projectile might have struck the windshield (photo) of Amtrak train 188 just minutes before it crashed, and investigators said that they had called in the FBI to analyze the damage.
Officials of the National Transportation Safety Board could not say whether engineer Brandon Bostian had been struck or incapacitated by a projectile.
The surprising revelation at a recent news conference significantly expands the scope of the crash investigation beyond either mechanical failure or operator responsibility.
Two other trains a, SEPTA commuter train bound for Trenton and an Amtrak Acela arriving from New York City were struck by projectiles in North Philadelphia shortly before the Amtrak wreck.

The New York Times also has an article by Dave Philipps and Elizabeth Harris about the problem, titled Rock Hurling Is Old Nemesis of Train Crews:

Though being struck by flying objects is typically not a serious safety concern, it is a common occurrence for train crews. 

Rico says they'll undoubtedly find some surveillance footage of some young punks tossing chunks of concrete off an overpass somewhere; a little late, but charging them with murder should inhibit a repeat performance... (And while Bostian was undoubtedly startled when whatever it was hit his windshield, it should not have caused a crash.)