Would a death without a physical reason be okay or too unrealistic? (low fantasy)

Just have him die. In real life people die without explanation all the time. Ever hear of SIDS, Sunden Infant Death Syndrome. That's where a baby dies and the medical examiner has NO CLUE what the kid died of so they put SIDS on the medical report (by law in most jurisdictions there must be a cause listed or the case will never be closed). And in a low fantasy setting where medical knowledge would be less (though many parts of the world actually had very detailed understandings of disease and other illnesses) it was clearly God's will or the work of witches. Maybe throw a scene in there where everyone suspects foul play but the king/queen/whatever's personal physician assures everyone that he just died of natural causes or something.

 

honour killing?