Someone who I met and spent a few days with died very suddenly and I truly do not know what to do

Ok the title kinda says it all, but I went to this program and spent a week with about 2 dozen others. We all got to know each other fairly well over that week and all had fun, all coming from different parts of North America.

That was early June of this year. I had heard that one of them had fallen badly ill, so I recently decided to check their Instagram page and their tagged section was filled with posts from their close friends about how they will be missed and that they're in a better place now.

It doesn't take much to surmise that this person had suddenly passed away. I don't think any of the others who did this program know yet? I myself am shocked and don't exactly know how to feel, I had only known this person for less than a week and yet I can't get them off my mind. Like it was just a few weeks ago they had been completely healthy and now they're gone.

I just... need advice on how to feel in this situation. We had only recently exchanged numbers and yet our conversation lies blank now.

It's such an eerie and bizzare feeling.