hang on, don't call the police yet......your star didn't kill him.
We have had our star for 2 years and has never killed anything.
the trigger was probably sick and lodged himself in the rock.
CC star will eat (or try to) a dead fish. We had a coral beauty for awhile and seemed healthy. One day he went missing. "Chip"
hadn't moved in awhile, so we moved him off the rock and sure enough, there was the fish and Chip was trying to eat him.
Fish will sometimes die without us visually seeing them sick.
Sorry for your loss
but your star was just doing what a carnivore does. They will eat up your reef, but doubt a moving fish. How long did you have the trigger?
hope you were kidding on killing him.....if you really don't want him give him to your LFS