Creating a Shortcode for Twitter Bootstrap Carousel (Slideshow)

I am trying to create a shortcode that I can use to create a Twitter Bootstrap Carousel that displays a slideshow of images from my WP database. At this point, how the images are stored in the database is flexible, I want to do whatever works best.

The shortcode I have created doesn’t seem to be working right… things are outputting out of the order I coded them in. For some reason, the_title() and the_excerpt are outputting before the <divs> that I have them wrapped in. Here is my code;

function bs_carousel($atts) {
   // Set Shortcode Attributes
   extract(shortcode_atts(array(
      'posts' => 1,
   ), $atts));

   // Start the Return String
   $return_string = '<div id="myCarousel" class="carousel slide">
 <div class="carousel-inner">';

   // The query
   $the_query = new WP_Query(array(
    'category_name' => 'Home Slider',
    'posts_per_page' => 1
    ));

   // The loop
   while ( $the_query->have_posts() ) :
      $the_query->the_post();
      $return_string .= '<div class="item active">'.the_post_thumbnail('large').'<div class="carousel-caption">
    <h4>'.the_title().'</h4>
    <p>'.the_excerpt().'</p>
   </div>
   </div><!-- item active -->';
   endwhile;
   wp_reset_postdata();
   $the_query = new WP_Query(array(
    'category_name' => 'Home Slider',
    'posts_per_page' => $posts,
    'offset' => 1
    ));
   while ( $the_query->have_posts() ) :
   $the_query->the_post();
  $return_string  .= '<div class="item">'.the_post_thumbnail('large').'<div class="carousel-caption">
    <h4>'.the_title().'</h4>
    <p>'.the_excerpt().'</p>
   </div>
   </div><!-- item -->';
   endwhile;
   wp_reset_postdata();

   // Finish the Return String and Clean Up
   $return_string .= '</div>
 <a class="left carousel-control" href="#myCarousel" data-slide="prev">‹</a>
 <a class="right carousel-control" href="#myCarousel" data-slide="next">›</a>
</div>';

   return $return_string;
}

add_shortcode('carousel', 'bs_carousel');

Any ideas what I’m doing wrong?