this is a hard question?

People have made the assumption that you meant to say "how can a deaf guy say your mother is dead to a blind guy" not "how can a dumb guy say your mother is dead to a blind guy".

As heartbreaking as the scenario is regardless of their situations it would obviously be much easier I hope, for a dumb guy to tell a blind guy him Mom was dead. I would hope they had an established friendship already, as I do not see a dumb guy selecting his words carefully. But if they are friends it would make things easier in what would be a difficult time. As for a deaf guy telling a blind guy his mom was dead...something so terrible really would only be told by one close to the other, not a stranger. If this were the case, I believe their communication difficulties would already have been worked out. Now the real question...did you intend to say dumb?

He can write it on a piece of paper, and then ask someone else to read it aloud to the blind guy. Alternatively, he can learn braille alphabet, and write it down that way so the blind guy can "read" it.

He can just tell it, as he is only deaf and not dumb.