'If you are reading this, I have successfully killed one of you. And I'm guessing they look VERY beautifully gruesome.

This was all but a trick. 
A trap.
I sent letters to you all, and you all then became wounded in my beautiful spider web. Being the curious morons you are, you came without a single thought! You didn't even question it! Didn't your mother ever tell you NOT to go to a party from an invitation from a person you don't even know?? Probably not.
But besides from that, now that I have you caught in my inescapable web, I shall kill you all. Picking off every. Single. Last. One of you all. Go ahead! Scream in terror! Regurgitate! Feel FEAR! No one will be able to hear you! And doing those actions will only make my time of murder more wonderful than it already feels! I will enjoy your last moments with your screams of pain and agony.
Until then...

Au revoir!~ <3' 

(She's reading a note that the murderer left them in a body!!)

(Sound like your being honest.)

"I don't have any, besides. Your mask is like a pair of sunglasses to be honest."

or

"....Seeing their actions, we know a little more on how NOT to get killed and have the other person scavenge inside our bodies for something to help them out of their situation of being stuck in a room, covered in blood."

(Say it either coldly, or with no emotion)

"Do as you please."