No idea about scarlet's ( we don't really get them here in Aus) but yesterday I literally sat and watched a new yellow leg hermit dig a much smaller nassarius snail out of the sand, flip it over and start prying it out of it's shell. This was after I'd found another empty nassarius shell on the sand. Plenty of food and empty shells in the tank and both snails were smaller than the hermit so I think it was just meanness.
I have another smaller hermit in the same tank who's been a model citizen for ages. When I dropped the new hermit in the tank, the first thing he did was chase the smaller hermit half-way around the tank, snapping his claws like a lunatic. I could sense the fear and panic in the smaller crab! At that point I had a feeling he was just a bad dude.
Needless to say he was banished and fortunately the snail survived... one of them at least. The thing with hermits is you just don't know what you'll get. Some are fine, content to graze on the rocks and mind their own business, others just wanna be bad.
