I think the killer is Shalini Malhotra...somehow I had a hunch about this for long time, in today's episode when Vasudha came with Shalini...DRS pointed at her..i think he meant to say she is the killer
may be she got Sushant's gun somehow..and just went and shot her..may be Sushant knows about this, but just trying to save her...Wat do u guys think??