Pom pom crabs aggressive?

[GreenSpottedPuffer]

I have a small pom pom crab that has "attacked" my small pearly jawfish twice in the past 2 nights or mornings. Yesterday morning and again this morning, I have found the jawfish out of his cave (never comes out), curled up in the corner of the tank with what look like sting marks on his body. Both times, the pom pom crab is in his cave!

Eventually the crab leaves and the jaw seems to go back but he is starting to look a little stressed out.

How normal is this? I thought they just used the anemones to defend themselves but I think he is clearly using them to "attack" in this case.