In tragic news that stunned Glee fans and Hollywood, the 31-year-old was found dead in his Vancouver, Canada hotel room on Saturday, 13 July, after failing to meet his check-out time. He had been staying at the hotel since 6 July.
Police have said foul play is not suspected but the cause of death was not immediately apparent. An autopsy will take place today (15 July).
Director Adam Shankman, who has helmed episodes of Glee, has told CNN that Cory was in good spirits when they spoke on the day of his death.
"I had several interactions with him yesterday where he told me he was feeling amazing, he even said I'm feeling fantastic again," said Adam.
"Like everybody else, I'm really devastated and confused by what happened."
Cory had been open in the past about his struggle with substance addiction, recently completing a second stint at a rehab facility.
"[Cory] has voluntarily admitted himself to a treatment facility for substance addiction," said a rep at the time. "He graciously asks for your respect and privacy as he takes the necessary steps towards recovery."
After leaving, Cory had tweeted on 26 April: "Sending out big love to everyone. thank you for the continued support! It means the world to me! :)"
The Canadian-born star had been dating his Glee co-star Lea Michele, who had stood by him during his treatment.
In a statement at the time she said: "I love and support Cory and will stand by him through this. I am grateful and proud he made this decision."
Since news of his tragic death broke, the star's rep has issued a statement requesting Lea be given "privacy" as she grieves.