I agree with DPete. Don't look like anything I would not load on. Looks to me like the front scraper had just lifted up to transfer loading to the back. Maybe he lifted the can too high, and then looks like he spun tires and slid down over the small windrow and that, coupled with the can too high, upset things.
I have had operators do the same thing, and with the same results. Usually operator error is involved, but then again, the boss should not have them on a slope if they don't have the skills. Problem I have had is the ones you tell to stay off the edge sometimes do it anyway to show you they can. Then when they tip it over, they get fired, but it is too late for the scraper, and the mechanics are going to be mad.