I can't bring myself to believe people who say they know not what to do when confronted with such a scenario.
1. Call the police
2. Call the hospital/clinic
3. Call emergency services
People who won't get in touch with the authorities only have things to hide. If the death is really accidental or natural, there shouldn't be a need to hide. It may be painful to go through the interrogation but innocent people will pass it without incident.