How do I make amends to this guy I hurt in the past?

A guy who I worked with a few years back told me recently that he was secretly in love with me but that he never had the guts to tell me. He said he found me quite intimidating. However, I don't understand why he thought this, because we used to joke and talk a lot. He's 10 younger than me, and I merely saw him as a younger brother, then. I had no idea about his feelings. I keep thinking about how I must have hurt him by certain things I might have said or done, so much that when I gave my notice and found out I was leaving he avoided me and stopped talking to me completely. I did not think much of it back then, as I was too excited about my new job to care about anything else. We got back in touch now, and I feel so guilty I can barely hold back my tears when I think about it. He's a lovely guy, he's so popular, everyone loves him. He's got a beautiful heart. What can I do to make up for all this? It really breaks my heart to think that he suffered because of me and that he might hate me for having hurt his feelings.