Who is right?

shlosmem

OK, I figure it out myself.
We can't assume that the "back end" of the train stops immediately when the engine stops.
But if we look at the engine distance from the flashlight according to the passenger point of view, the distance is 1.9 km, but like mpv_plate mention there is a "ground expanding" factor which is 1/0.435889=2.294162 if we multiply this factor on our 1.9 we get 2.29416*1.9=4.35889 the same distance the observer on the ground see.