Writing a condolescence letter

I've written out the envelopes.

I can see the family before me.

I've known the family for more than 30 years.

Yet I can't find the words to express my feelings about Steven's death.

I knew he was ill. I knew at the holidays he was very ill and was getting hospice care.

What are the right words to share at long distance about the loss of an acquaintance, the parent of your daughter's close friend.