Can a married Indian man marry an American woman without divorce?

This is a very sensitive issue for me. Without going into personal details (Im not the husband/wife). A married Indian man left his wife and son to work in USA in 1999. Due to recession, he rarely sent money to support his family. Neither did he visit India nor did the family went and visited him during this time. The man left no property/financial assets since the couple lived at wife's maternal home. In 2009, his wife called up the man and a woman picked up. She and the man said that they are now about to be officially married and he has/will soon get his green card. To keep sending some minor amount of money, he blackmailed the wife to sign some legal papers that he will be sending through post. The wife reluctantly did that. And the man is now married. The American wife has her own daughter from previous marriage. How is this possible? What kind of legal papers were they? Can an Indian man in any circumstances get a divorce from Indian wife without entering the country? Since those papers did not have any alimony settlement... the man rarely sends her money. But since then her son is older and is handling the finances. Will he/the mother have any legal disadvantages in future?