NV Amtrak Crash Update

There was really no news coming from the crash site in Northern Nevada involving a semi truck and an Amtrak train. However, the death toll is now up to 6 people. There are several people who are unaccounted for.
However, some questions need to be answered.
First and foremost, why did the passenger cars of the train start on fire and why did the train go up in flames so fast. Granted, there were no close emergency services like a fire department or ambulance service close by, but why did the train go up in flames so fast?
Was it something in the train or the truck that caused the fire?
Second, it seems strange that the trucker began skidding 50 yards ahead of the train crossing and wasn't able to stop in time. The truck was a gravel truck but it was empty. Unless the driver was going a very fast at the time, that should have given the driver time to stop in time if going the speed limit or have a slow speed impact with the train. It also seems strange that the driver hit the 3nd or 4 car in the train, which seems to be strange as well. As a former volunteer firefighter, I have seen car/truck vs train accidents and everytime, the engine hit the car. I have been on train rides and have been been on trains in accidents and again, the engine has hit the car or truck. I have also read many stories about car/truck vs trains and almost always it is the engine that gets hit. The times when another train car was hit, most of the times, it was decided it was a suicide or deliberate. But in this case, there were skid marks, which makes this case strange.
http://www.rgj.com/article/20110625/NEWS/110624030/Amtrak+train+crash++Death+toll+up+to+6
So, we need to know more information, especially about the driver, before we know what happened at the crash site.