Meh.

To be fair what the guy told you can assume to have been told in confidence; so you can't really go and tell your manager the details and hold the moral high ground.

What I don't understand is why your colleague hasn't contacted the manager and told him he can't come to work. That's just weird.

Can you contact the colleague or his family? Tell them they have to ring the boss and call in sick, tell him they're having a family situation or whatever...

If they don't do it, you have to and you can say he's having some "family crisis" and say that you don't feel at liberty to say more. But if pressed I suppose you have to report what you've seen at work.