How to write in firebase from directive

I'm try to write something to firebase from directive

This is my directive [UPDATED]:

angular.module('MyApp.directives').directive('score', function() {
    return {
      restrict: "E",
      scope: {
      },
      templateUrl: 'dashboard/score.html',
      controller: ['$scope', function ($scope) {

      }],
      link: function(scope, element, attrs, controller, firebase) {

          var eventsRef = new Firebase('https://URL.firebaseio.com/');
          scope.event_id = attrs.index;
          //Score counter
          scope.Score = [0, 0];
          scope.add_btn = function(num) {
            scope.Score[num]++;
          };
          scope.dist_btn = function(num) {    
            if (scope.Score[num] > 0) {
              scope.Score[num]--;
            } else {
              num = 0;
            }
          };

          scope.setPrediction = function () {
            eventsRef.child('/'+scope.event_id+'/').update(scope.Score);
          }
        }
      }
});

And it's throw error:

FIREBASE INTERNAL ERROR: Server Error: ClientId[7373865]:ErrorId[2]: Error on incoming message

Ok I realize wats happend. Firebase don;t like to post arrays without key's

This code is working:

angular.module('MyApp.directives').directive('score', function() {
    return {
      restrict: "E",
      scope: {
      },
      templateUrl: 'dashboard/score.html',
      controller: ['$scope', function ($scope) {

      }],
      link: function(scope, element, attrs, controller, firebase) {

          var eventsRef = new Firebase('https://sportsbettr2.firebaseio.com/events');
          scope.event_id = attrs.index;
          //Score counter
          scope.Score = [0, 0];
          scope.add_btn = function(num) {
            scope.Score[num]++;
          };
          scope.dist_btn = function(num) {    
            if (scope.Score[num] > 0) {
              scope.Score[num]--;
            } else {
              num = 0;
            }
          };

          scope.setPrediction = function () {
            eventsRef.child('/'+scope.event_id+'/').update({
                "score": scope.Score
            });
          }
        }
      }
});