How do I find out how my father died in assisted living, if nobody will answer my calls?

My 67 yr old father, who was healthy other than being a stroke survivor and not being 100% mentally sound, just mysteriously died on May 27th. Nobody will tell me how he died. I've left messages with his guardian and she won't answer me. I can't even leave a message on her specific line as the phone system is screwed up. There's no way to put in extension. I'd like answers...