Because it sounds logical for me :) For example, why is my shadow following me, but other guys don't have a shadow? Ok, only I have a shadow, but why is it killing only me? So, that's why I supposed you did it. Like you all game hiding from the guards, you agree with feeling fear front of guards, that twist, when the shadow started killing not only you but guards can flip the gameplay and can be described as developing of the main character. I hope I described the idea clear :)