31-year-old Cory Monteith was found dead in his Vancouver, Canada hotel room by cleaning staff on Saturday, 13 July, when he failed to meet his scheduled check-out time.
Glee co-stars have been speaking out in the past day about their shock at the tragic news, which came shortly before filming on the fifth series of the comedy was scheduled to start.
Darren has not been active on his Twitter account since the news, but he remembered Cory on the Girl Most Likely red carpet in New York last night by pinning a black ribbon to his suit jacket.
An autopsy on Cory was carried out by the Coroners Service of British Columbia today, after it was fast-tracked because of the intense public interest. It's thought results could be available as early as today but if they prove inclusive, a report could be delayed until toxicology results are confirmed.
Police said at the weekend no foul play was suspected but an apparent cause of death was not immediately clear.
A statement from Glee's executive producers and Fox read: "Cory was an exceptional talent and an even more exceptional person. He was a true joy to work with and we will all miss him tremendously.
"Our thoughts and prayers are with his family and loved ones."
Cory had been dating his co-star Lea Michele, who is said to be "devastated" by the tragedy and has requested privacy.
More reactions from Glee stars:
Dot-Marie Jones: "My heart is broken. Cory was not only a hell of a friend, he was one amazing man that I will hold close to my heart forever. I am blessed to have worked with him and love him so much. My heart is with his family and our whole Glee family. I love you all."
Damian McGinty: "The guy I shot my first acting scene with. The nicest guy I've met. Can't believe it."
Harry Shum Jr: "At this time, please send nothing but love and light. This tragic news still doesn't seem real to me. I love you Cory."
Matthew Morrison paid tribute to Cory during a concert in New York, saying although it was "awkward" to perform so soon after his friend's death, he would dedicate the night to him.
Naya Rivera: "Cory was and always will be a part of my own family and a good friend. He was a special part of this world and will forever be missed. My heart goes out to Cory's family and Lea and while we are grateful for everyone's well wishes, privacy during this time of grief is greatly appreciated."