Sorry...

Sometimes it's a dilemma whether to say sorry or not... You do regret doing something which might have hurt someone, but what if that person clearly doesn't like to talk about the topic. I know it sounds a bit vague, let's just have a look at my case.
So there's this guy in my class who is usually very involved in whatever we do as a group, talks quite a lot, makes jokes now and then... Just a typical fun classmate. But last week he looked a bit off. Before class had started, some of my mateys and I we're talking about our plans to go to Nickerie with the whole group. So when he arrived, we excitedly told him about the trip, but his reaction was cold. We instantly noticed his outfit: a fancy longsleeve shirt all buttoned up, different shoes, shiny watch AND he had shaved! Now that would explain his behavior: He was going on a date! The most natural thing to do was to start asking questions about who and where and we kinda started teasing him. He kept saying it was nothing, but nobody believed him. Later in class even my teachers (I can't call them professors right...) noticed that he was acting a bit different and even they made a joke about his "date", saying he looked a little nervous. At the end of the day he still didn't wanna tell us and we all went home that evening.
The next day I asked another classmate of mine if she knew what was up with him the day before. She said she didn't know exactly, but as far as she knows him, he does take distance when being teased. Okay so then I knew I shouldn't be making stupid jokes with him.
Three days later we we're in the same building. We would be the only two attending class (cus the others would prepare for their exam the next day). Since we were alone, I dared to ask him again about that day. Explaining the outfit he told me he had to go to his cousin's birthday dinner. I thought it was weird, cus birthdays are supposed to make you happy, and he obviously wasn't. So I asked him why he was being that silent then, on which he answered that thát was something else he wouldn't wanna share.
Later that evening something popped into my head! I could remember something happened 3 years ago, but I wasn't so sure of it. So yesterday I googled around and found out that on that exact day his brother (I think) died in an accident. I felt a little bad. I would've felt horrible if I had lost someone so dear to me while others were making a joke about it.
So I gotta say I'm sorry! It was none of our intention to laugh about something so serious. But I still have my doubts...

Xx