Don't intend to throw cold water on anything... But
Nurses and EMTs do not pronounce or confirm people dead in cases like this.
SOPs when witnessing someone going down is to ensure an open airway, check for breathing, check for pulse, proceed to CPR. In my experience CPR is administered no less than 15 minutes or so but most likely longer, most often until the patient is in the hospital and and doctor orders discontinuation.
IMO, the medics and nurses present did not do their job if they did not immediately check Airway, breathing, circulation followed by CPR.