ok now it's obvious, erika is the culprit with the complicity of a servant (kanon).
Erika said in purple that if someone gets killed then he will die. so someone can be killed and die later.
Murders:
1st twilight:Erika and kanon killed the servants and kinzo,erika was the 7th woman and kanon fake his death.
George and hideyoshi:kanon killed them,he is a servant so can use the wirecutter
Natsuhi and jessica:kanon hide in the garden shed,meanwhile erika forced natsuhi and jessica to be caged in the garden shed so kanon can killed them.
Kyrie and rudolf:all others were outside so an easy murder.
Kanon killed them and escape from the window then erika put another sigil on the window to subtitute the one break by kanon.