My best friend died this morning. I really need advice on how to tell his mother.

I just found out my best friend died this morning. He was rushed to the hospital this morning and later died. His fiance has asked me to pick up his mother at the airport later this afternoon. His mother as of this writing, has just taken off to fly to visit myself, my best friends fiance and her son. She doesn't know her son has died and I'm not sure what the best action is when I pick her up at the airport.
I found out he died after I texted his mother that I'll pick her up. What should I do? What should I say?
The mother knows her son has been in and out of the hospital for the past several weeks. She's going to be devastated that her other son has died.


Source.