Capture Coordinates in Google Map on User Click

You should add the click listener on marker will give you the position of marker.

//Add listener
google.maps.event.addListener(marker, "click", function (event) {
    var latitude = event.latLng.lat();
    var longitude = event.latLng.lng();
    console.log( latitude + ', ' + longitude );
}); //end addListener

Edit:
You need something like this

//Add listener
google.maps.event.addListener(marker, "click", function (event) {
    var latitude = event.latLng.lat();
    var longitude = event.latLng.lng();
    console.log( latitude + ', ' + longitude );

    radius = new google.maps.Circle({map: map,
        radius: 100,
        center: event.latLng,
        fillColor: '#777',
        fillOpacity: 0.1,
        strokeColor: '#AA0000',
        strokeOpacity: 0.8,
        strokeWeight: 2,
        draggable: true,    // Dragable
        editable: true      // Resizable
    });

    // Center of map
    map.panTo(new google.maps.LatLng(latitude,longitude));

}); //end addListener