What cut my finger ?

I had a new coral fall from a rock, I put my hand in to pick it up and some
under a rock which I assume was a shrimp popped it nipper out and with a
loud crack sound it got me between the wick of my thumb nail and the skin,
it drew blood real fast. Not to meantion it scared the **** out of me and I
bumped a rock while pulling my arm out and the whole rock wall come tumbling
down.

I got the rock wall back up but not the way it was originaly, but I am still
guessing the attack was from a mantis shrimp.

Anyone want to guess what it was ?

-Andrew