Adding Vector Data - GML format with WFS Transport (possible bug?)

I'm trying to add features to my OpenLayers map, by querying a publicly available WFS server which serves GML data.

// initalize the map
var map = new ol.Map({
    layers: [
        new ol.layer.Tile({
            // OpenLayers public map server
            source: new ol.source.OSM()
        }),
    ],
    target: 'map',
    view: new ol.View({
        // center on Murica
        center: [-10997148, 4569099],
        zoom: 4
    })
});

var xmlhttp = new XMLHttpRequest();

// execute this once the remote GML xml document has loaded
xmlhttp.onload = function() {

    console.log("GML XML document retrieved.  executing onload handler:");
    var format = new ol.format.GML3();

    var xmlDoc = xmlhttp.responseXML;

    console.log("you will see multiple features in the xml: ");
    console.log(xmlDoc);

    // Read and parse all features in XML document
    var features = format.readFeatures(xmlDoc, {
        featureProjection: 'EPSG:4326',
        dataProjection: 'EPSG:3857'
    });

    console.log("for some reason only a single feature will have been added: ")
    console.log(features);
    console.log("Why is this?");

    var vector = new ol.layer.Vector({
        source: new ol.source.Vector({
            format: format
        })
    });

    // Add features to the layer's source
    vector.getSource().addFeatures(features);

    map.addLayer(vector);
};

// configure a GET request
xmlhttp.open("GET", "http://geoint.nrlssc.navy.mil/dnc/wfs/DNC-WORLD/feature/merged?version=1.1.0&request=GetFeature&typename=DNC_APPROACH_LIBRARY_BOUNDARIES&srsname=3857",
   true);

// trigger the GET request
xmlhttp.send();

Here is a CodePen with the bug demonstrated.

http://codepen.io/anon/pen/yamOEK

Here you can download it packaged into a single HTML file: https://drive.google.com/open?id=0B6L3fhx8G3H_cmp1d3hHOXNKNHM

I can successfully download an entire feature collection with multiple features into my variable xmlDoc, using a valid typename. However, when I use format.ReadFeatures(xmlDoc), the OpenLayers GML format parser appears to only be extracting a single feature from the feature collection, whereas it should be extracting many more.

It would be wonderful if someone could take a look and see if they can figure out if I'm doing something stupidly wrong or it's a legitimate bug in OpenLayers3. Thanks so much for anyone who's able to help!

Single feature is added because entire document is read so instead of format.readFeatures(xmlDoc) parse each feature.Here is source code:

    var vector;
    var map = new ol.Map({
        layers: [
            new ol.layer.Tile({
                source: new ol.source.OSM()
            }),
        ],
        target: 'map',
        view: new ol.View({
            center: [-8197020.761224195,8244563.818176944],
            zoom: 4
        })
    });

    var xmlhttp = new XMLHttpRequest();
    xmlhttp.onload = function() {
        var format = new ol.format.GML3();
        var xmlDoc = xmlhttp.responseXML;
        vector = new ol.layer.Vector({
            source: new ol.source.Vector({
                format: format
            })
        });

        for (var i = 1; i < xmlDoc.children[0].children.length; i++) {
            var features = format.readFeatures(xmlDoc.children[0].children[i], {
                featureProjection: 'EPSG:4326'
            });


            features.getGeometry().transform('EPSG:4326', 'EPSG:3857');
            vector.getSource().addFeature(features);
        }

        map.addLayer(vector);
        map.getView().fit(vector.getSource().getExtent(), map.getSize())
    };

    xmlhttp.open("GET", "http://geoint.nrlssc.navy.mil/dnc/wfs/DNC-WORLD/feature/merged?version=1.1.0&request=GetFeature&typename=DNC_APPROACH_LIBRARY_BOUNDARIES&srsname=3857",
        true);

    // trigger the GET request
    xmlhttp.send();

Here is a CodePen result. http://codepen.io/anon/pen/bwXrwJ