How to retrieve users from specified radius in GeoFire?

Question

I have an android app which shows user's markers in nearby location to mine with specified radius. For example: I set radius on 1 km, and I would like to retrieve all users which are in this radius. At now, on a map I have markers but I would like to also display users. How could I do that? I can not see any specific documentation to allow get users from radius in GeoFire. Using Map, I can count amount of markers.

I have in a database user child also, which display name, nick etc. Should I use this part to display users' nick in this radius?

Here is my code:

     ref_red = FirebaseDatabase.getInstance().getReference("geofire/red_marker");
     geoFireRed = new GeoFire(ref_red);
     geoQuery = geoFireRed.queryAtLocation(new GeoLocation(lat, lng), km);

        geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {
            @Override
            public void onKeyEntered(String key, GeoLocation location) {

               geoItems.setText("Somebody is here. " + String.valueOf(markers.size()));

               Marker marker = mGoogleMap.addMarker(new MarkerOptions().position(new LatLng(location.latitude, location.longitude))
                        .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED)));
                markers.put(key, marker);

                tvDetected.setText("Object detected." + String.valueOf(markers.size()));

            }

            @Override
            public void onKeyExited(String key) {

                geoItems.setText("Nobody is here. " + String.valueOf(markers.size()));

                Marker marker = markers.get(key);
                if (marker != null) {
                    marker.remove();
                    markers.remove(key);

                }         
            }

            @Override
            public void onKeyMoved(String key, GeoLocation location) {

                Marker marker = markers.get(key);
                if (marker != null) {
                    marker.remove();
                    markers.remove(key);
                }
            }

            @Override
            public void onGeoQueryReady() {

            }

            @Override
            public void onGeoQueryError(DatabaseError error) {

            }
        });

And here is my part of geofire database:

Could someone help me to resolve this problem?