In my opinion the motive was to kill Hemraj .After watching and reading various theories I think peoples involved in murder consumed liquor in hemraj room and then went to roof and killed Hemraj by hitting him from behind and as they were going back arushi got woke up and opened the door of her room and when they saw arushi they hit him on head from front and then cut her neck,
there are many stories we often read where Thieves clear the house when whole family is sleeping in next room.
