• Michelle Trachtenberg has died, an NYPD spokesperson confirmed to Business Insider.
• The 39-year-old actor was known for roles in "Buffy the Vampire Slayer" and "Gossip Girl."
• She made her film debut as a child actor in 1996, playing the title role in "Harriet the Spy."

Michelle Trachtenberg has died at age 39.

A spokesperson for the New York Police Department told Business Insider that Trachtenberg was found dead at One Columbus Place, a luxury high-rise apartment complex near Central Park in Manhattan. Police had responded to a 911 call at about 8:01 a.m. and found Trachtenberg unconscious and unresponsive. She was pronounced dead at the scene.

The New York Post and ABC earlier reported the news, citing police sources.

According to the authorities, the death is not being treated as suspicious. A cause of death hasn't been determined.

A representative for Trachtenberg didn't immediately respond to a request for comment.

The former child actor was best known for her roles in "Buffy the Vampire Slayer," "Harriet the Spy," and "Gossip Girl."

Born on October 11, 1985, Trachtenberg began her career as a child actor at age 3. She started off in commercials, with her first on-screen appearance in an ad for Wisk detergent.

After bit parts in the second season of "Law & Order" and "Clarissa Explains It All," Trachtenberg landed her first regular role as Nona F. Mecklenberg in the second season of "The Adventures of Pete & Pete," appearing on the show from 1994 to 1996. She also appeared on the soap opera "All My Children."

Trachtenberg's breakthrough came when she was cast as the title character in "Harriet the Spy," which marked her feature film debut. Her performance as the titular 11-year-old aspiring sleuth won Trachtenberg a Young Artist Award for best leading performance in a feature film.

As a young teen, Trachtenberg returned to the small screen with "Buffy the Vampire Slayer," in which she played Dawn Summers, the younger sister of the title character played by Sarah Michelle Gellar.

Trachtenberg's character was introduced in the show's fifth season and quickly became a pivotal part of the teen supernatural drama, earning her a Teen Choice Award nomination for choice TV sidekick in 2001 and maintaining a main role through the series finale in 2003. For many fans, Dawn Summers remains the role for which they know Trachtenberg best.

However, her time on the popular show was not without its difficulty.

In 2021, Trachtenberg said there had been a rule that series creator Joss Whedon wasn't allowed to be in a room alone with her. She made the claim, which Whedon later denied in a New York Magazine interview, amid reports of Whedon's alleged history of abusive on-set behavior from other former "Buffy" stars like Charisma Carpenter.

Trachtenberg remained close with several of her "Buffy" costars, including her former on-screen sister, Gellar. In January, she posted a throwback photo of herself with Gellar in honor of Woman Crush Wednesday. "Slay all day! Always loved this twinning photo of us!" she captioned the picture.

After "Buffy" concluded, Trachtenberg continued to appear on TV and in film throughout the 2000s, with recurring roles in the series "Six Feet Under," "Weeds," and "Robot Chicken" and memorable appearances in movies like "Ice Princess," "EuroTrip," and "17 Again."

In 2008, Trachtenberg landed her second career-defining role, as conniving rich girl Georgina Sparks in The CW series "Gossip Girl."

Trachtenberg's Georgina appeared in a recurring capacity through each of the series' six seasons, quickly becoming a fan-favorite as she battled for supremacy against Leighton Meester's Blair Waldorf.

The actor called Georgina, which earned her another Teen Choice Award nomination for choice TV villain in 2012, one of her favorite roles and relished playing a villain. "It's definitely a lot more fun than playing the good girl. I love the reaction you get. I never understood why some actors don't want to play villains or evil characters," she told Seventeen magazine in 2009.

In 2022 and 2023, she returned as Georgina in the second season of the "Gossip Girl" sequel series on Max. It was her last credited on-screen appearance.

Additional reporting by Natalie Musumeci.