Locomotive front and back, I think.
So, if train was moving left to right in the wide angle photo, this would be the rear locomotive after having pushed the cars past the accident scene after the accident.
The left (zoom) photo must be from the other side of the tracks than the wide angle, so the train would have hit the truck as the truck was crossing from the left to right on the wide angle photo.
That makes sense to me, since the damaged truck was where the people are standing.
The trailer was further down in the direction of train travel in the wide angle, so the train must have hit the trailer, separated it from the cab on impact and dragged it down the track until the trailer flipped on the steep embankment.
That it was makes sense to me, but only speculation., based on the photos alone.