Nicholas Brendon and Alyson Hannigan has shared emotional tributes to their late Buffy the Vampire Slayer co-star Michelle Trachtenberg.
The 53-year-old actor posted a live video on Facebook in which he reacted to the news that Trachtenberg had died on Wednesday aged 39.
"I didn't see her much after Buffy, a couple of events together, but when we were working together she was just like a beam of light," he said, his voice thick with emotion. "I think it was just the last thing I expected, not that I was expecting anyone to die. But I really am sorry to her family."
Alluding to his health issues and history of substance abuse, he added, "I thought I would have gone first. It's a tragedy."
He wrote alongside the video, "Just heard the news about Michelle. Still processing. She was a ray of light on set and will be missed."
In the popular TV series, Trachtenberg played Dawn, the younger sister of the title character Buffy Summers, played by Sarah Michelle Gellar. Brendon and Hannigan played Buffy's best friends Xander Harris and Willow Rosenberg.
Alongside a series of photos of her and Trachtenberg, Hannigan wrote on Instagram, "I am deeply saddened by the news of Michelle's passing. She brought a loving energy to the set of Buffy. My thoughts are with Michelle's family and friends."
Their tributes follow posts written by co-stars David Boreanaz, James Marsters and Emma Caulfield, who wrote, "I'm so sorry your bright light died so young. Our Buffy family lost a little sister today... Rest in peace lovely Mish Mish. You were loved."
Gellar, who is developing a revival of the show, has yet to publicly address her on-screen sister's passing.
Trachtenberg, who was also known for Gossip Girl and Harriet the Spy, was found unresponsive in her New York City apartment on Wednesday. Her exact cause of death is currently unknown, however, she reportedly underwent a liver transplant last year.
