How should i act when someone stutters

How should i act when someone stutters On new year's eve a friend introduced me to some of his friends and one of them had a stutter. I think I unintentionally made him uncomfortable and now I have a few questions. Generally: Do you guys want people to ask you how they can help you feel more comfortable or would you prefer them not addressing your stutter? He only had that stutter when talking to me and not while taking to his friends. Is is because he is more comfortable with them already? Or is it maybe because I'm a woman? (All other people I saw him interact with were guys, so I can't make any generalizations.) Or is there certain behavior by other people that triggers stuttering? I asked a question in a round of 5 people and one guy answered and then looked at him - like requesting him to answer, too. He started answering me and was stuttering very strong to the point where it looked like he was in physical pain. (It looked like his facial muscels were cramping.) The other guys exchanged some knowing looks and then I just interrupted him mid-sentence after a minute because I felt like I was torturing him. I smiled while interrupting him and was just like "that sounds great!" even though he didn't get to the point yet and then I just changed the topic completely. From reading some posts here I know now that was probably the worst reaction possible. So should I address this now when talking to him next time and apologize? Or would that be even weirder and I should just not interrupt him anymore from now on? And is it really that bad if people finish your sentences if they surely know what you want to say? I'm generally a fast speaker and know what people want to say after half their sentence no matter whether they stutter or not, so I often interrupt people and tell them they can interrupt me back or should tell me if I interrupt them to often. They usually say that they are fine with that. Should I be more sensitive if people are stuttering or can I do this with them, too?