A Nightmare

Rainbow unicorn addresses the crowd of unicorns (not pictured) that have come to marvel at the burning corpse.
There has not been a unicorn murder for as long as anyone can remember, and Old Blue was a wise and well respected member of the unicorn community.
This tragedy has sent the community reeling; if the perpetrator is not found the unicorns will surely be killed off one by one.
Already the rainbow unicorn has noticed several clues... most unwelcome clues.