Get first image in ACF repeater field

first-acf-repeater-image.php

		<?php 
		$first_img = true; 
		while($first_img && has_sub_field('post_images')): ?>
		
		    <a href="<?php the_permalink(); ?>">
			    <img class="img-responsive" src="<?php
			    $image = get_sub_field('image');
			    echo $image['sizes']['blog-lg'];
			    ?>" alt="<?php echo $image['alt']; ?>" />
			    <?php $first_img = false; ?>
		    </a>
		
		<?php endwhile; ?>