As sdgraham said, to declare/pronounce someone dead may be done only by one having legal authority such as a coroner or doctor. Obituaries and the like announce deaths.
In Dallas ,Texas the doctor attending slain president JFK pronounced him dead at 1:00 pm local time. The news reporters immediately announced his death to a horrified nation.
My mother, a doctor, once attended a fatal road accident outside our house. She could do nothing for the driver of the crashed car.
The police asked her if she would 'pronounce life extinct' and she duly did so.