I have to disagree on that; loading the crossbow requires two hands yes, but it was already loaded. Since it's a light crossbow he can fire it with one-hand. It's explained here;<br/><br/><div class="quoteheader"><div class="topslice_quote">Quote</div></div><blockquote class="bbc_standard_quote"><strong>Light Crossbow [Simple Ranged Weapon]:</strong> The string is pulled back by using a hinged lever which pulls the string into place. Despite its name, this weapon does not have the “light” property. It is the least expensive crossbow (25 gp) and does good damage (1d8) at a reasonable range (80/320). It requires two hands to load or to attack with this weapon, but it only weighs 5 pounds and can be carried in just one hand.</blockquote><div class="quotefooter"><div class="botslice_quote"></div></div><br/>Source: https://olddungeonmaster.wordpress.com/2016/12/19/dd-5e-crossbows/<br/><br/>I definitely agree with you if he wants to use his crossbow again and needs to reload it, though. In that case he'd have to drop his shield first, but right now he doesn't since he already had a free hand.<br/><br/>