Murderer talking to someone..

I think we are all forgetting.. that the murderer said that He wants to kill A virani.. then he singles out Nandini.. and even sends her a note.. to meet outside.. so how can it be sahil killed tripti or anyone from SN be the killer.. SURE.. it acn be on accident that Tripti was killed.. but it cant be a planned murder by someone from SN.. what say?? 😉