Matt, I'm sorry for the loss of your friend.
The Police are conducting an investigation. At this point you may be a suspect, either in his death, or something (drugs, theft) related to his death. I would suggest you make some notes to your self on the time frame of your contacts with him. Specifically, the times of your phone calls to him that were answered by someone else. They may get a search warrant for your phone, which means you lose your phone for awhile.
Not sure how things work in your county/state, but I don't think the police will act as probate investigator or probate court. A probate investigator has probably already secured his stuff, and is trying to locate next of kin. You may want to get in touch with the probate investigator and let them know what you know of his family.
Once again, sorry for your loss.