crab died and turned mushy?

[cornflakes]

One of my red clawed crabs died probably a few days ago....I didn't know until yesterday when i what looks like arms from the crab floating around the tank. When I found him, he was pale and had a very nasty smell and when I took him out, he literally melted and turned to goo.

I saw him alive a few days earlier and he looked to be fine. When crabs die, do they always turn to mush and goo or was it just because he was in the water?