Well, we now may know why Robert Pattinson says he won’t marry girlfriend and Twilight costar, Kristen Stewart, anytime soon.

US Weekly reports that the actress was paparazzi’d in a few “steamy rendezvous” photos with her Snow White and the Huntsman director, Rupert Sanders.

A source tells People: “Kristen is absolutely devastated. It was a mistake and a complete lapse in judgment.” The source adds, “She wasn’t having an affair with Rupert. It was just a fleeting moment that shouldn’t have happened. She never meant to hurt anyone. She’s a good person who just made a bad choice.”

A rep for Sanders, who is married and has two children, could not be reached for comment. Stewart’s rep has had no comments.