The actress, best known for her roles in Gossip Girl and Buffy the Vampire Slayer, has passed away unexpectedly, leaving the entertainment world in shock.Michelle Trachtenberg was discovered unresponsive by her mother around 8 a.m. on Wednesday, February 26, at One Columbus Place, a luxury high-rise near Central Park in New York City, according to police sources. She was 39.The NYPD responded to a 911 call reporting an unconscious woman at the residence. In a statement to People,

authorities confirmed, “Upon arrival, officers observed a 39-year-old female unconscious and unresponsive. EMS arrived on the scene and pronounced the victim deceased. Criminality is not suspected.”While an official cause of death has not yet been determined, sources revealed that the actress had recently undergone a liver transplant. The investigation remains ongoing.