Here we go, the final chapter/ending. Have fun!
Once the lights are turned back on, Cadance turns to everyone while saying sheepishly, "Sorry about that. Didn't mean to scare anyone."
"Too late for that!" Spike scowls angrily.
"And then, there were three more murders, which leads us to now."
"So who did it?!" Everyone else yells out impatiently. The time for the murderer to be revealed is now!
"How about we consider each murder one by one, shall we?" Cadance ask sternly as she strides away then stops in one certain lizard doctor. "Dr. Lizardo! You knew all enough that Diamond Tiara was still alive. Even psychiatrists like you can tell the difference between patients who are alive or dead, not even by mistake! So when you fired the gun at her in the dark missed, you pretended that she was dead and made up that somepony tried to take the gun from you to avoid suspicion. This give you the chance to kill her later, unobserved."
"She's right! He was missing in the kit