Engine shut off while accelerating, engine will crank but not start

I was increasing my speed to get up to the posted speed limit after leaving out of a drive away with a steep downhill grade I was using my lower gears first, and second to come down the hill before entering the highway and accelerating to get my speed up to the posted speed limit allowed. When I stopped at the bottom of the hill, I put the van back into D and stopped completely before entering the highway to accelerate to 50MPH as posted, but I only accelerated to 30MPH and heard very loud clunking between the front seats of the van. Then, I put it N and tried to get it to start. But it only cranks and won't start.