media_handle_sideload() returned post_id being incremented

Question

Okay I hate it when I just figure it out after I post the question.

But it seems each post can have a number of attachments. Which means each attachment has an ID associated with it. Which was confusing because it shared the same ID style and type as the post.

The following code is able to get the URL of the associated uploaded image

$media = get_attached_media( 'image', $post_id ); 
foreach($media as $image) {
  $url_img = wp_get_attachment_image_src($image->ID,'full');
  echo $url_img[0];
}