Such incidents of massive sheep fatalities are unfortunately frequent in the Pyrenees Mountains in summer time, when sheep are left feeding in mountain pastures. Incidents are usually triggered by brown bears (fully protected by law in France) preying on sheep, then entire flocks stampeding and sometimes jumping off cliffs. Even Great Pyrenees dogs commonly used for protecting flocks cannot always keep bears away. Wolves (also fully protected) are not yet a major problem in the Pyrenees but are already a serious one on the French side of the Alps Mountains.
Louis