A lot of you have speculated on the theory as to why Sameer is marrying Shikha and then taking her life.
Maybe, he has made out an insurance policy in her name and made himself the benefactor. It must be his sinister way of making money by marring a person and killing that person for the Insurance policy. From one wife to the the next! This has happened a lot in the west (I am a fan of 20/20). The fact that he was calling someone on the phone and saying that he would join this person soon, is an indication that he has an accomplice who is helping him in this crime. Also means that it will happen very soon.
The fact that he has changed is name, made his fake family vanish and moved to an unknown secluded location points out to his devious intentions.
Did he make the call to his in-laws with his own phone? Don't think so.
Whatever the motive, its far more interesting than the saas bahu story line