bp_document_user_messages_delete_attached_document( $thread_id,  $message_ids,  $user_id,  $update_message_ids )

function bp_document_user_messages_delete_attached_document( $thread_id, $message_ids, $user_id, $update_message_ids ) {

	if ( ! empty( $update_message_ids ) ) {
		foreach ( $update_message_ids as $message_id ) {

			// get document ids attached to message.
			$document_ids = bp_messages_get_meta( $message_id, 'bp_document_ids', true );

			if ( ! empty( $document_ids ) ) {
				$document_ids = explode( ',', $document_ids );
				foreach ( $document_ids as $document_id ) {
					bp_document_delete( array( 'id' => $document_id ) );
				}
			}
		}
	}
}