Dear NAME

We are [shocked and] sorry to hear that your [relation], DECEASED, has passed away. We would like to express our deepest condolences and sympathies [of all of us at ACCOUNT_JOB_COMPANY] to you and your family. 

We know that DECEASED will be greatly missed.

We understand that words are not much comfort and hope there is something we can do that would soften your grief. Please do consider us your friends and let us know if we can assist you in any way. We will stand behind you and provide our full support all the way.  

Sincerely yours,

........................................