spain. first of all the pictures are extraordinary. walk us through this. what actually happened? reporter: that cctv footage surveillance cameras, a few yards from where actually the train crashed into that concrete column. it doesn t have any audio it s cctv footage but what our eye is drawn to of course is the locomotive the back end seems to swing out from the tracks and that crashes into the concrete column the back part of a bridge and goes on its side and brings the rest of the train with it. if you go back a fraction of a second before that happens, you can make out a puff of something, is it a puff of dust, is it a puff of smoke?