If a loved one has died and you aren't sure what debts they had, you may want to get a copy of their credit report(s) in order to try to figure that out.
This is not always a simple process, and can be very stressful if you are grieving. But it can be helpful down the road if you are trying to settle their financial affairs.
The first step is to gather documentation you'll need to prove that you are handling their estate as the executor or personal representative. Usually this will be in the form of letters testamentary available through probate court. You'll also need certified copies of the death certificate.
Next you'll need to request the credit report from one or more of the three credit reporting agencies. (While they should have similar information, it's possible there are debts reported to one or two of them but not all three, so it's not a bad idea to get them all.) You'll want to send a signed request along with your documentation mentioned above. Send your request using priority mail or certified mail. That way you'll have tracking so you know it's been received.
Equifax, P.O. Box 105139, Atlanta GA 30348-5139
Experian, P.O. Box 2002, Allen TX 75013
TransUnion, P.O. Box 2000, Chester PA 19016
Credit reports won't necessarily list every debt but it should give you a pretty good idea of outstanding debts so you can contact those creditors.
For more information on how to cope with the debts of someone who has died, read: Dealing with A Deceased Person's Debt