William felt the magical backlash a second after Nate noticed it and took the initiative - wartime instincts; William felt shaken enough when one of the staff reacted, but it was even worse when it was someone still technically a student - but he wasn't fast enough to do anything fancy like banish the wand or try to dispel the wild magic.
Nate had the other two girls; William grabbed the third, now shocked out of continued tears, and shoved her toward Nate while he whirled to shield them with his body and throw the broken wand into an empty corner of the room.
He didn't quite make it.
The wand exploded just as William let go of it, shattering into billions of tiny fragments. Luckily the magic had gone rogue and hungry; it ate up the wooden housing in a burst of flame and smoke almost instantly. There was nothing but a cloud of debris left in the air, thicker than dust and with a distinctly magical feel to it. What was left of the backlash, perhaps. William made the mistake of trying to breathe and coughed as the stuff burnt his lungs, gasping for a few seconds before the cloud dissipated and the smoke disappeared.
William felt a little dizzy, but mostly relieved. "Is everyone all right?" he asked Nate, turning around and catching himself on the nearest stone limb when the world tilted slightly sideways. He shook his head to clear it and focused on the cluster of girls under Nate's protection.