I think what happened is like this.Hemraj invited Krishna and RajKumar for drinks.After having few drinks animal instincts of Rajkumar arose and he went to Aarushi's room and tried to rape her,she resisted and he kills her,meanwhile Krishna is witness to this and after that they both run away.Meanwhile Talwar wakes up and come to Aarushi's room and realises that Aarushi is dead and suspects Hemraj and kills him.As such from point of view of Talwar's they have lost their daughter,but at same time because of a murder committed at a fit of anger may land them in jail,so they tried to destroy evidence and also tried to mislead police
