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They are the killers surely
They acted too cleverly and destroyed all the evidence
The reason that i believe that they killed Arushi and Hemraj is that only four people were in the house .
Two died and two were alive ...The door was locked from inside and Rajesh Talwar ...Nupur Talwar and Arushi's dead body was inside ...Who else could have killed her and bolted the door from inside is the question that needs to be answered if they are not the killers