Actress Michelle Trachtenberg, best known for her roles in “Buffy the Vampire Slayer” and “Gossip Girl” has died at the age of 39.

According to ABC News, the actress was found dead in her New York City apartment early Wednesday morning by her mother. A police source told the news outlet Trachtenberg had recently undergone a liver transplant and had been experiencing complications.

An autopsy will be conducted by the medical examiner’s office to determine the cause of death; however, it is believed that Trachtenberg died from natural causes and there was no suspected foul play involved.

The New York City native was a child star best known for her roles with Nickelodeon, and the series “The Adventure of Pete & Pete” and the film “Harriet the Spy.”

Michelle Trachtenberg’s breakout moment came when she landed the role of Dawn, the younger sister of Sarah Michelle Gellar’s character, on “Buffy the Vampire Slayer” (2000-2003). This role earned her a Teen Choice Award nomination for Choice TV Sidekick in 2001.

From 2008 to 2012, she portrayed Georgina Sparks on “Gossip Girl,” a role that got her nominated for Choice TV Villain at the Teen Choice Awards in 2012.

She also made a cameo in the music video for Fall Out Boy’s hit song “This Ain’t a Scene, It’s an Arms Race” in 2007.

X users took to social media to show their sympathy at the news of Trachtenberg’s untimely death: