Even if a rock or something had hit the windshield, I don't understand how that would have made the train accelerate its speed like it did. Accelerating the train's speed requires changing the throttle position, a very deliberate action, and the acceleration lasted several minutes. Also, from the pictures I've seen, the projectile didn't even go thru the glass, so it didn't hit the engineer or any instruments. It crackled the glass at the impact point but didn't penetrate it.
Also, authorities said that they didn't see anything hitting the windshield on video that they checked.
Strange. 
