Maria Shriver "Horribly Shaken" By Son's Accident

Maria Shriver has been at the bedside of her 13-year-old son Christopher Schwarzenegger ever since the youngster suffered internal injuries during a boogie boarding accident a week ago. Understandably, the incident involving her youngest child was particularly upsetting to Maria.

"She was shaken horribly," says a source close to California's former first lady, who was with Christopher on the Malibu beach when he was injured by a powerful wave.

"This is her baby," the source continued. "She has been at the hospital nonstop, 24-7. She is sleeping there. How much can she take right now?"

Christopher, who was admitted to an L.A. hospital with a collapsed lung, broken bones and broken ribs on July 17, is improving and is expected to be released by mid-week.

Fortunately, the mom-of-four has a strong support system. "It's very hard on Maria but her friends and family are there with their love and support," says another source. "All the kids are visiting – they all adore and love each other and they are all there for each other."

Also part of that support system: Maria's estranged husband Arnold Schwarzenegger. "Arnold is a great father," says a source close to the family, "and he and Maria will always come together when it comes to supporting and loving their children."