(CNN) Jenny Mollen and her family have had "a traumatic week."

The actress best known for her role on the TV series, "Angel," revealed that she accidentally dropped and injured the 5-year-old son she shares with husband Jason Biggs.

"On Saturday evening, I dropped my son on his head causing him to fracture his skull and landing him in the ICU," Mollen wrote in the caption of a photo of her holding her son on her Instagram account. "I am forever grateful to Lenox hill downtown and @nyphospital for their immediate response and aid."

Mollen and Biggs have two boys: 5-year-old Sid and 1-year-old Lazlo. The couple obscures their children's faces when they post about them on social media.

It was Sid who was hurt, and Mollen offered a "Thank you to all of the nurses, neurologists, pediatricians, residents, cafeteria staff and brave women that keep the visitor's bathrooms clean."

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