This story left some important things out. He and his family probably went to US to visit relatives of his wife. He decided to stay in America because he was not happy with his life in China.
How did he get his green card? There is only one way that is political asylum. It is ironic for a hero from China to apply for political asylum in US.
Anybody from China can apply for political asylum with the help of a crooked lawyer from Chinatown. We will never know what reason he used to apply for political asylum.
"I hereby declare, on oath, that I absolutely and entirely renounce and abjure all allegiance and fidelity to any foreign prince, potentate, state, or sovereignty, of whom or which I have heretofore been a subject or citizen; that I will support and defend the Constitution and laws of the United States of America against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I will bear arms on behalf of the United States when required by the law; that I will perform noncombatant service in the Armed Forces of the United States when required by the law; that I will perform work of national importance under civilian direction when required by the law; and that I take this obligation freely, without any mental reservation or purpose of evasion; so help me God."