Ed Hoffman, also known as Demon Archer, is the culprit of all three deaths of Crispin Addley, Ms. Kee and Vince Wrainwright.
Around a year before all of this action, Forensic Invesigator Luke Harding sabotaged Ed's javelin in the competition He was taking part in.
Now, Ed wanted his own back so he had murdered these innocent people and framed Luke for it. He had managed to do this by choosing to kill people that Luke may have a grudge against.As well as this, every weapon that was used had a relation to diamonds such as a glass cutter, the weapon used to murder Vince, has an edge that is made of tiny diamonds.The reason for this is that Luke has the nickname 'Diamond' amongst the instructors of the school.
At the end of the story, Ed attempts to kill Luke but fails as Luke's best friends- Malc and Jade Vernon step in and save the young investigators life. This was done by Malc jumping in front of Luke and Jade using her newly invented 'spotlight sound' to point it straight at Hoffman and turn up the volume to ear splitting loudness so that it made him fall to the floor. After that, he was arrested.