It is hard to see the falsh in frame 4 but you do nitice it on the video. Almost like his brake lights coming on but that can't be because the car goes dark right after.
If you play the video full screen from 14sec thru 17sec one split sec at a time. You will see a flash then complete darkness and then the explosion. What that means to me is something blew up that knocked out power completely, no brakes lights, no headlights, nothing, then the crash.