Absolutely call him to see how things are. I will pray that she is okay. This is a totally different set of circumstances, and because you had a relationship with both him and his family, the support you give is needed and natural.
Right now, his thoughts are about his sister, but you can take the opportunity to be a friend, someone he can lean on. Sending a card to his sister would be wonderful.
Inability to look usually means they do not want to show how they are feeling. I suspect he wanted to just have someone hold him so he could cry, but men have that "macho" thing. Let him know you are there for him, and if he needs a shoulder, yours is available.
I am so sorry about his sister. It is a hard thing to go through.
You in the alt?
Im still standin better than I ever did looking like a true survivor feeling like a little kid Im still standin after all this time and Im picking up the pieces of my life without you on my mind..