Michelle Trachtenberg’s death at just 39 years old has shocked both her fans and former collaborators. But those who encountered her in her final days say the signs were there that something was very wrong.

Blake Lively and Alyson Hannigan are among the former "Gossip Girl" and "Buffy" actors mourning the death of their one-time co-star, Michelle Trachtenberg.

Michelle Trachtenberg was found in her New York City apartment, and the death is not believed to be suspicious, police said.