Writing a condolence letter is not easy but is very important. It is a written reminder of your support and help that gives some relief to the sufferer. In the letter offer your condolence and sympathy. Express your feeling about the deceased and mention his personality. It is better to keep the letter short and meaningful. In the end extend your condolence to other family members too.
Here is a sample formal condolence letter:
Mr. John Macbeth,
I would like to express my sincere condolences for the unexpected death of your father. On behalf of the entire office, please accept our sympathy. I can only imagine what a difficult loss this will be for you and your family.
Though I did not know your father except for few occasions when I got a chance to know his kindness and great thoughts. Just in those few moments I was highly impressed by his views and ideas.
You must proud that god had blessed you with such a great personality. I understand that words are not enough to heel this great loss but you need to keep patience.
All the members of the team have sent their sincere sympathy to you and your family. Please pass on our commiserations to your family and friends.
May you all get some comfort in this difficult situation?