Hayden Panettiere's Death at 36 Leaves Rosie O'Donnell 'Heartbroken' as Stars Flood Social Media With Tributes

Hayden Panettiere passed away at a tragically young age of 36, and now Hollywood is flooding her social media with tributes.

One of these was Rosie O'Donnell, who wrote, "Oh my god – heartbroken #hayden," as reported by Deadline.

While complete autopsy and toxicology reports from the Greenville County Coroner's Office are currently awaited, initial reports revealed that Panettiere was found unresponsive at a residence in Greenville, South Carolina, on August 16.

As reported by TMZ, authorities were alerted to the medical emergency by a 911 call from one of Panettiere's friends.

First responders reportedly attempted to resuscitate her using "advanced cardiac life support," though the police refused to confirm this.

After chest compressions administered by paramedics failed as well, Panettiere was reportedly pronounced dead at 2:32 p.m. She leaves behind her daughter Kaya, 11, shared with former fiancé Wladimir Klitschko.

In a statement to People, her representative said on behalf of her father, Skip, "It is with profound sadness that we share the tragic passing of our beloved Hayden."

"She was an incredible light and a force of nature who brought immeasurable love and joy to all who knew her — and to the millions who watched her onscreen," they added.

David Arquette and Melissa Barrera, both of whom were Panettiere's costars from the Scream franchise, also extended their heartfelt tributes to the late actress.

Arquette, for one, posted, "I love you Hayden," while Barrera wrote, "Rest in peace sweet Hayden."

Selma Blair, who had an uncredited role in Scream 2, also said, "I love you. Don’t be gone. Please," before reportedly following up with two similar messages.

Viola Davis, who worked with Panettiere on Architect and Custody, wrote, "What an amazing talent you were….so gifted. Julius [Tennon] and I loved working with you….an old, wise soul with such a deep heart."

She added, "I wish the world had more time with you because I had a burning curiosity about who you were becoming. I saw this beautiful Phoenix rising from the ashes."

Podcaster Jay Shetty, who discussed Panettiere's career and difficult personal life in an emotional interview a few months ago, also left a message for her.

He said, "I can’t believe it. Our friendship had just begun and I was so moved by the conversation we shared earlier this year. My love and condolences to her family and fans."

Bethany Joy Lenz left a lengthy message for Panettiere, writing, "I’m crushed. I knew the wild little blonde. Was she nine? Ten? I was eighteen. She ran through the Screen Gem studio hallways at 222 E44th St. laughing and playing games in between blocking and camera rehearsals. Long, unruly curls trailing behind her."

"She knew her lines and everyone else’s. Her intelligence was astonishing. She understood scenes and nuance and human struggle like no child I’d ever seen on camera. And she’d sit with you for a great conversation, then giggle and go play," she added.

"We’d connect on and off over the years, like the cousin in the family reunion who got famous and life moved her away — but I always felt such joy seeing her when we were lucky enough to cross paths," Lenz concluded.