With the scene laid out I’ll put some non exhaustive examples of how dunnit (culprit may not refer to murder, ie culprit of a prank):
- Everyone there was involved, they all lied to Erika (under the assumption the detective’s authority can’t force the culprits to speak the truth) and Erika did not examine the corpses.
- Above, except Erika did look at the corpses and was fooled because of movie makeup, fake corpses or an illusionist trick
- Some of the people were culprits and lied to Erika, and some didn’t hence they witnessed the corpses and were fooled
- The victims weren’t culprits but were unconscious and not dead
The point about the how dunnit is the implications:
If the solution is used were they all lie to Erika, then automatically everyone involved has to be a culprit. However that means a motive has to be assigned to all these people and a time when they met and conspired for this scene.
If only some lie, then the innocent must have witnessed and been fooled by the corpses.
The preparation time and materials for making a corpse realistic enough to fool someone is much longer then the time to just lie to Erika.
If someone somehow can create a valid theory of the victims being actual victims, then explaining the disappearance requires more detail.
This particular mystery allows for the simplest solution, but my point is that each how dunnit has implications that have to link together with all the other mysteries in the game. All culprits will need a motive and all plans will need preparation. Waving off a mystery as accident reduces the implications one can gather to piece together the entire thing.