Did you have a clean up crew and/or live rock with potential hitchhikers in place? It's amazing how quickly they can break things down. I know that in the recent power outage, I had 4 fish (only had 4 in the tank) die...3 of them more or less in unreachable places unless I wanted to rip my rock apart. One of them was in view, but out of reach - and I watched as in around 36 hours start to finish the various crabs, shrimps, and other assorted nicknacks and doodads shredded him down to nothing.
I'm pretty sure one of the scarier things I've seen is a bristle worm on a mission.
firefish, ocellaris clown fish
caulastrea, green star polyps, palythoa, zoas