Moriarty thinks of Sherlock as his property. Nobody else is allowed to touch him, mess with him, play with him, etc. He is extremely possessive of him. Sherlock is the same way with him - though it is in a much more subtle way.
Then, he finds out that CAM raped Jim. How he finds out is up to anon (maybe CAM was boasting about it, like he boasted about flicking Janine in the face?), but he is furious. This is the real reason behind him shooting CAM at the end of S3E3.
How Jim reacts to learning the real reason behind CAM's death is up to anon, but I'd like a somewhat happy ending. In-Character, Vulnerable!Moriarty is love!
Moriarty/Sherlock, Non-Con CAM/Moriarty, Sherlock's Turn to Save Moriarty
Then, he finds out that CAM raped Jim. How he finds out is up to anon (maybe CAM was boasting about it, like he boasted about flicking Janine in the face?), but he is furious. This is the real reason behind him shooting CAM at the end of S3E3.
How Jim reacts to learning the real reason behind CAM's death is up to anon, but I'd like a somewhat happy ending. In-Character, Vulnerable!Moriarty is love!