Scaring the guests with those fake hippos that popped out of the water in Pirates of the Caribbean/killing them with heavy cleats.
They killed the black hippos by bludgeoning them with heavy cleats. 
mnli hypothesis: They killed the black hippos by bludgeoning them with heavy cleats.  premise: Scaring the guests with those fake hippos that popped out of the water in Pirates of the Caribbean/killing them with heavy cleats.