Usage patterns
〈数〉人の死者a given number of dead/casualties
Fifty deaths were confirmed in this accident.
死者を弔うto mourn/hold a memorial for the dead
The bereaved family holds a memorial for the deceased every year on this day.
死者を追悼するto pay tribute to / commemorate the dead
A time was set aside at the ceremony to commemorate the war dead.
Expressions
死者を出すclaim lives; cause deaths; result in fatalities