map.js

function (doc, meta) {
  if (doc.Type == 'killed') {
    emit(dateToArray(doc.Time), {Attacker: doc.Attacker.Class, Victim: doc.Victim.Class, Weapon: doc.Weapon});
  }
}

reduce.js

function(key, values, rereduce) {
  var result = {};
  if (rereduce) {
    values.forEach(function(v) {
      for (var attacker in v) {
        result[attacker] = result[attacker] || {};
        for (var victim in v[attacker]) {
          result[attacker][victim] = result[attacker][victim] || {};
          for (var weapon in v[attacker][victim]) {
            result[attacker][victim][weapon] = result[attacker][victim][weapon] || 0;
            result[attacker][victim][weapon] += v[attacker][victim][weapon];
          }
        }
      }
    });
  } else {
    values.forEach(function(v) {
      result[v.Attacker] = result[v.Attacker] || {};
      result[v.Attacker][v.Victim] = result[v.Attacker][v.Victim] || {};
      result[v.Attacker][v.Victim][v.Weapon] = result[v.Attacker][v.Victim][v.Weapon] || 0;
      ++result[v.Attacker][v.Victim][v.Weapon];
    });
  }
  return result;
}