Can someone please explain...?

*please read all the way to the end*. So my dad is in a band with a few of his friends, and I’m pretty close with them and I hang around them a lot. On monday morning, his lead vocalist, Antney, had a heart attack and he’s been in a coma ever since. Knowing that he’s such a great guy, and that hes like a second dad to me, I’m really hurt by this. I’ve only known him for about 2 years, and everyone thinks I’m crazy for grieving over someone I haven’t even known that log. Am I? Anyway, ever since finding out what happened to Antney, I’ve been really stressed and emotional, more than I typically am. I did research because I’m, quite literally, a hypochondriac, because lately I’ve been noticing a change in how I feel. My heart PHYSICALLY hurts, there’s “pressure” and tightness in my heart and it just physically hurts when I breathe. I’ve never felt anything like this until yesterday, pretty much. I didn’t think anything if it yesterday because I just thought I could sleep it off or something. But it’s not going away. As I was doing research, it said that emotional altercation can cause physical damage too. I’ve never heard of such a thing. Can someone explain that for me? Maybe it’s just a placebo thing because I’m worried about him and I’m scared it’ll happen to me, but I really don’t jniw how to feel right now. Explain? Thank you