How to reopen a child custody case? child custody Divorce?

Hi we live in Houston Texas and I have a friend that had just lost her child custody to her ex-husband..she had said at court that she wanted to leave him because he was violent and because he would do alot of drug they both got tested and he came out positive on alcohol and drugs, a couple of years back he was deported to Mexico because of money laundering there was a police report done that he had pointed a gun at her....can any one tell me what went wrong? can it be reopened?