NRI husband

My sister has been married to an NRI on 2012 may. He was there in india for 15 days and went to usa. From then there is no site of him. And after 1 yr of marriage he is saying that he is not interested in my sister and he wants divorce. We have a doubt that he must be married to another girl there because their parents hurried there visit to usa in 2014.. my sister is so innocent and frightened to file a case against him. And now taking that as weakness he had prepared certain possibilities and frightening us. For past 5yrs there is no site of him but now he is out with some sh*t statements against us.. so that he can escape safely without any mud to his clothes..