Theres been a death in the family.
Heres how i think it went down, either one of 2 ways, first one was that the urchin caught the cleaner ratting him out about stabbing some coral with his spines, so he took him out.
second way, the classic falling piano, the cleaner shrimp was cleaning the sand minding his own business eating algea, while the urchin got himself upside down and couldnt hold on anymore, and fell, luckily for the urchin the shrimp was their to break his fall, poor cleaner, but to not get caught he is trying to finish him off and get rid of the evidence, but i caught him just the same because he takes to long to eat stuff.
or third it was a molt, but i had a feeling this guy would die for some reason, but if in a couple days i spot him cool, if not oh well, have to get me another one day, not anytime soon though.