Hermit Crab shell stealing?

I have an orange legged hermit that i've had for a while now. I moved him over to my newer tank from my older one.

I added three more hermits - two blue legged and one red legged.

Soon after I added the new ones, one of the blue legged ones died, I thought it just shed it's exoskeleton but it's dead.

Today I just noticed that the orange legged hermit is now in the red legged hermit's shell...leads me to belive it's killing off my hermits, and has stolen the shell of the red legged one.

Can't see the reg legged one anywhere...

Do hermits become agressive to one another and kill each other off?

 

If they like the shell enough they will kill snails, so I don't see why it wouldn't kill off smaller crabs for their shells

 

Yes they will, you need to provide a selection of shells to help prevent this