Just stand there with your mouth hanging open

From Create Your Own Story

You can't believe it, you're too stunned too move. You realise you're drooling, staring at her juggling breasts your hand creeps down your body into your pants. You begin masturbating to your mother, you know it's wrong but that just makes it hotter. The man lifts your mother up as he furiously rams his dick into her pussy. As he lifts her up she opens her eyes and spots you! Shit, busted. What do you do?