Placing a Facebook screenshot in the FB.Feed after grabbing it with FB.API?

I'm using FB.API to grab a screenshot of my game, but I don't know how to retrieve the photo ID to put it as a link in FB.Feed. I've heard that you can grab the photo ID from the Callback in the FB.API, but I'm unsure how to do that. Anyone have any insight on this?

Code I'm using (C#):

 private IEnumerator TakeScreenshot() 
 {
     yield return new WaitForEndOfFrame();
 
     var width = Screen.width;
     var height = Screen.height;
     var tex = new Texture2D(width, height, TextureFormat.RGB24, false);
     // Read screen contents into the texture
     tex.ReadPixels(new Rect(0, 0, width, height), 0, 0);
     tex.Apply();
     byte[] screenshot = tex.EncodeToPNG();
 
     var wwwForm = new WWWForm();
     wwwForm.AddBinaryData("image", screenshot, "InteractiveConsole.png");
 
     FB.API("me/photos", Facebook.HttpMethod.POST, Callback, wwwForm);
 }