It probably became an irrevocable trust when he died. 

Was there a capital gain (maybe not, with stepped-up basis)?  Was there other income to the trust after his death?  Did the corporation pay rent to the trust, before and/or after his death?  Will the widow receive a Schedule K-1?  Is she even your client?  Had he been filing joint returns?  Is she filing Canadian tax returns? Did he live in a community property state?  Did they have a marital agreement?  Do you really want to get involved with this?