According to People, a "distraught" Kristen broke the news of her "huge mistake" to Rob shortly before the story went public.
"Telling Robert was the worst thing she's ever had to do," sighs a Stewart snitch.
He was "blindsided" by the betrayal and felt like he'd had his "heart ripped out."
"There was no sign that either of them was unhappy," observes a Pattinson spy. "He would have done anything for her."
Now, an insider tells Us, he "doesn't know what to do."
Despite Stewart's "pleading" texts and phone calls, Pattinson has reportedly cut off contact with his girlfriend of three-plus years and asked her to move out of the Los Angeles home they share. Word is, he's also maintained custody of their dog, Bear.
Kristen, meanwhile, has been leaning on longtime friend Jodie Foster, claims Radar Online.
"As soon as she heard the news, Jodie contacted Kristen to offer her support," says a snitch. “They have been close friends since they starred opposite each other in the 2002 movie 'Panic Room,' and Jodie is a mother-like figure to her."
Foster is supposedly "disappointed" with Stewart, but she knows, at 22, she's still very young, and unfortunately people make mistakes in life. She thinks Kristen will learn from this and will only grow into a more mature person because of it."