Robert Pattinson and Kristen Stewart Credit: George Pimentel/WireImage; Andreas Rentz/Getty

Is this the twilight of Twilight's golden couple?

After Kristen Stewart was caught cheating on Robert Pattinson with her Snow White and the Huntsman director Rupert Sanders, the future of young Hollywood's hottest pair has become extremely blurry.

Hiding out since the news broke late Tuesday, Pattinson is "really depressed," one source close to the actor, 26, tells Us Weekly. "He doesn't know what to do. He doesn't know if he should forgive her or not."

Stewart released an emotional, contrite apology to the world Wednesday afternoon, and behind closed doors is "devastated," another source close to both stars says. "She's very angry at herself. She's really not blaming anyone but herself."

As exclusive photos in the new Us Weekly reveal, Stewart, 22, and Sanders, 41, had a marathon makeout session while out and about in Los Angeles July 17.

"Rob is beyond devastated," a third source adds. "He's so heartbroken. He's shocked she could hurt him and humiliate him this way."

First romantically linked in 2009, the Twilight costars have slowly begun sharing their real-life romance with the world-- with pals recently telling Us Weekly that Pattinson was mulling a marriage proposal and Stewart dreaming of starting a family with her man.

"Rob's whole experience of coming into fame was experienced with Kristen," says the first source. "This is going to be really tough. Nobody knows if they'll stay together at this point."