If the deceased was only an acquaintance, you can send this polite, sympathetic condolence letter.
Dear {Recipient},
I am so sorry for your loss. Everyone I know has always told me about how delightful {deceased} was to have for a friend. I consider myself lucky to have met {him/her} and make {his/her} acquaintance, if only briefly, at {event}. I wish I had gotten the chance to know {him/her} better, because {he/she} was clearly very special and well-loved.
My heart goes out to you during this period of grief. Please call on me if you need anything at all.
Love,
{Sender}
