Goby multiple homocides?

Yes the tank is small (10g) but the fish were few, small and got along well. That's the usual story. The tiny neon blue goby did his thing, stayed out of site hanging on the side as he loved. Two red firefish added and they would stay in their bolt holes together, side by side. They seemed to enjoy each other's company. Not much else in there - a cleaner shrimp, bunch of snails and 3 tiny hermit crabs and a porcelain crab.

I woke up this morning to find one firefish on its side and the neon goby stiff as a board. Couldn't tell who was beating who up as there weren't many signs and a snail was already eating what it could of the firefish before I took it out. The only thing I can guess is that the neon was still trying to occasionally clean the firefish who didn't want to have any of it. The shrimp is smart enough to know that the firefish weren't really cleaner friendly. There were absolutely no signs of aggression or territorial issues as you could see generally with other fish, like clowns or damsels (cute, can be small but extremely territorial.) Is it possible that the neon and firefish went at it? Hard to believe the neon could take out the firefish. Or might it be the remaining firefish who committed a double homocide? This calls for Ace Ventura....