Hello tangomike,
I'm very sorry.
I had a similar experience. My senior year in college (1989-90), a freshman lived on our floor. We weren't close or anything, but we saw each other once in a while. As I recall, she was a vegetarian, mainly for moral reasons.
After I graduated, she transferred to another school, graduated on time, and went on to earn her doctorate and become a high-ranking scientist. Almost ten years ago, I decided to reconnect with her, and we exchanged a couple of emails and had an in-depth telephone conversation. She mentioned she'd previously been depressed, but seemed to have gotten better on a permanent basis. She also was buying a house with her boyfriend.
Imagine my surprise when, a few years later, I saw an article online dedicated to her memory. I contacted one of the authors, and was told she had taken her own life in November 2005.
Like I said, she and I were never close. But I do wonder sometimes if I'd kept in touch with her more often after our conversation, maybe just a time or three each year. Of course I'll never know, and odds are even if I'd done that it wouldn't have changed anything.
Tangomike, you mentioned mutual friends. Maybe you can reach out to them and see if there is anything you can do. You might even deepen or even possibly gain a friendship or two. And you may certainly appreciate the friends you have more.
Cheers,