Dear ______ (name),
I was just informed by our office manager of your _______ (relative’s) death.
It is impossible to adequately express my sincere sympathy at this most difficult time.
I had worked very closely with _______ (name) in the office. Therefore, I feel that I have lost a very good friend as well as a fellow co-worker.
Please let me know if I can be of any help to you.