Frogs and toads usually eat insects such as beetles. In this case, the beetle bites the back of the amphibian which responds violently by trying to shake off the predator. Once it has cut into the back, its prey is paralyzed and can be eaten at leisure.
The livescience.com site has a video of one attack. These studies were done at Tel Aviv University in Israel and there are no observations of this behavior in the US - so far.