A.K.A The Robber Crab
You guessed it – the coconut crab (aka the robber crab)! They found the missing Steyr rifle sometime later. The crabs dragged it off and crushed it.
There have been a number of reports of these crabs stealing shoes and cameras of tourists and locals that pass through and carelessly drop their things or leave them behind. This peculiar behavior becomes especially funny once you learn their age.