When you call 911, both the police and the paramedics will probably respond. Paramedics will treat a "non-attended" (non-hospice) death like any other patient at risk. They do not expect ordinary citizens or the family to be expert at determining death, so they will likely initiate emergency medical procedures. They will also probably take the person to the emergency room of the nearest hospital, where death may be officially pronounced by the emergency room doctor.
If your loved one has previously signed a Do Not Resuscitate order, or DNR, and you have the document ready to show the emergency personnel, they can forgo attempting cardiopulmonary resuscitation (CPR). However, they will probably still transport the deceased to the emergency room, so that the doctor may make the official death pronouncement.