Physician and a pilot... not sure what we are "arguing" about here.
If this was indeed a witnessed arrest, then it is a shame that no apparent attempt was made to lay the man down in the forward entryway and attempt CPR and at least attach the AED leads to see if there was a "shockable" rhythm. Any onboard MD, EMT, RN, fire or police, current or recent military could have possibly helped.
The fact that this did not happen makes me suspect that the event was not witnessed but merely discovered when to FO tried to wake the pilot prior to the beginning of the descent into BOS.