Uncaught SyntaxError: Unexpected token u

I am trying to get a JSON response from a get request. However, I am getting the following error: Uncaught SyntaxError: Unexpected token u. I know the rails route works because I do get the response loaded successfully in the Console.

The Ajax Response is supposed to start when the checkbox changes and is checked.

Why am I getting this error from the $.parseJSON?

Rails Controller

def providers
   @providers = User.order("last_name ASC, first_name ASC, middle_name ASC").where("provider_flag = ? and inactive_flag = ? and del_flag = ?", true, false, false).select("id, CONCAT(IFNULL(last_name,''), ', ', IFNULL(first_name,''), IFNULL(middle_name,'')) AS full_name");

    respond_to do |format|
        format.json { render :json => { :providers =>  @providers.to_json}, :status => :ok }
        # format.json { render :json => @providers.to_json }
    end
end

Javascript

$('#provider_chk').change(function() {
        if($(this).is(":checked")) {
            $.ajax({
                url: '<%= providers_schedule_index_path %>',
                type: 'GET',
                dataType: 'json',
                data: {
                    authenticity_token: $('meta[name=csrf-token]').attr('content')
                },
                success: function(data) {
                    console.log('loaded successfully.');
                    var providers = $.parseJSON(data.responseText)['providers'];
                    providers_count = $(providers).size();
                    console.log(providers);
                    console.log(providers_count);
                },
                error: function(data) {
                    console.log("An error has occurred!")    
                }
            });
        } else {
            $('#providers_results').empty();
        }
    });

JSON Response

providers: "[{"id":2,"full_name":"Test, User"}]"