Hermit Crabs Dying?? With Pics

[I'm Batman]

I have this massive Dwarf Zebra Hermit Crab named "Raper Crab," who goes around trying to rip crabs from their shells (even with shells that he's too big for).

 

 

Today I found him with his second Dwarf Red Tip Hermit, devouring it out of its shell.

 

I've recently started seeing a bunch of empty shells lying around.

 

Are they dying or being muck ducked?

 

any input welcome as always...