I have no clue how that happened. It looks like at least 2 vehicles were involved, one of them being a John Deere tractor.
I would say it was on a flatbed and its on the otherside but you just can't see it. The load wwas to high and the bridge snatched it off when he went under it. Just my guess though.
I don't think anything hit the top of the bridge. The top of the tractor cab isn't damaged and the bridge isn't scarred up. My guess is that the tractor was hit head-on by something going very fast. The front of the hood isn't damaged either, but if the tractor was turning left on the other side of the bridge, the other vehicle could have impacted the right front tire. The rear hitch on the implement dug into the dirt and stopped, so the tractor went over the top of it. Just my guess.