that this is what actually happened .

cop arrives on scene notices kids messing with shark after looking determines they were toying with something that was basically dead which incidentally he doesn't feel like moving up ,so he tells them to move it .

kids move it out of fear ,but get mad cause they had to move it and that they had gotten caught so to cover their tracks they tell what happened but conveniently left out the part where they were playing with a basically dead shark .