Always the same single post is shown

I created a custom post type with WordPress called “Members”. I just added two members:

1. John Miller
2. Mary Smith

No matter for which member I click on “View member” I always only see the page of the last member I added, which is Mary Smith. Also, when I enter the URL for my first member, John Miller, (www.example.com/?members=john-miller), I get Mary Smith as the result. How can this be?

In the single template file I have the following code structure:

<?php get_header(); ?>
<?php
    query_posts('post_type=members');
    if ( have_posts() ) : while ( have_posts() ) : the_post();
?>
<!-- content with content of custom fields in here -->
<?php endwhile; endif; wp_reset_query(); ?>
<?php get_footer(); ?>