Aaron turned back in shock when he heard Remus scream.

He witnessed it then, the change. It was horrific. More gruesome than anything he could have imagined. It wasn't a magical transformation, but a physical one. His bones broke and grew and grew back together in their new position. His skin strained, his muscles changed and hair grew from his skin.

Shocked and unable to move, Aaron witnessed the pain Remus was in. It was awful, but he wouldn't abandon him now.