Starfish Arm decay?

Well i did some more research, to no avail. It was spreading quick and he was losing two arms. I read that the most humane way to put him down (since i couldn't cut through him with the sharpest knife i had; believe me i tried; it was heartbreaking) was to wrap him in saran wrap and throw him in the freezer. Apparently they start to hibernate then die. So that's where he's ended up :-[ i still feel horrible. i hope whatever this was it doesn't harm my damsel or the eels.:-/