I came to know several of them, though not to the point of knowing any of them well. Tiananmen was such a serious event for these students. I know there was pressure on them to avoid any discussions related to the event and especially to to avoid any statements supporting the students who protested and died.
I had a conversation with one of these men that I knew best and whom I studied with and after all the geoscientific things had been beaten down until we felt we had achieved a deeper understanding of the topic, talk turned to world events. I didn't steer it in that direction, he brought it up after looking around to make sure that we were alone and especially that there were no other Chinese students in the room that might overhear. We discussed Tiananmen Square for a few minutes and at the conclusion he mentioned the fear that he had of discussing that subject with anyone. He had to be careful who he studied with and talked with as some of his fellow students were known to be strong supporters of the Chinese Communist Party and they would report anyone they determined to be supportive of the dead students. He told me that their families back home might suffer as a result. His absence of trust in those with whom he had the most in common - language, culture, etc really drove home the depth of the fear that he felt. Discussing that event with any of them was just not going to happen since he feared for his family back home.
You had to be there. There was so much positive change in the air back then with dictatorships under threat, communism being exposed and challenged, young people full of the knowledge that they could effect meaningful change in their lives if they were willing to take a stand or to fight for it.
Thirty years is a long time. It has certainly been plenty of time for the Chinese Communists to rise to their current status by adopting the things most useful in other systems while imposing an iron hand of control over the parts of the system that maintain their own power.
A number of these students stayed in the US or moved to the EU for employment in the industry after grad school. Others returned to China to help develop their domestic oil and gas industry.