[Golden Witch Drugs]

Oh, I have a theory Unfortunatly I couldn't take care of the small details, so this is just a rough theory.

Spoiler:

I belive that either Genji or Kanon are the culprits. First of all, Kanon didn't like that Shannon was going to marry George. But I do not belive that Kanon had the courage to murder anyone so I belive that Genji preformed everything. Genji, who is a servant, prepared the tea and drugged it so he could preform the first twilight. At the second twilight, I belive that Krauss shot Kinzo, and in Genji's anger he shot Krauss. (I belive there was another rifle somewhere or Genji used the same rifle and then put another rifle in Kinzo's hand) He made it look like he didn't do it in the last second before Rosa came. At the third twilight, I belive that something like Kanon and Shannon fighting leading to the discover of Genji's murderes. Genji needed to do something, since all the servants were there, so he killed them all. Then he discovered that there wasn't enough victims, so he sacrificed himself to release himself from he's sins. Well... This is kind of a bad theory, but it's the best I can come up with!