|Cory Monteith was found dead in his hotel room on Saturday|
The 'Glee' star, 31, who voluntarily checked in to rehab for a month to battle drug addiction and was released in April, was found dead in his hotel room in Vancouver, Canada, on Saturday.
The 'Stay' singer, 25, wrote on Twitter: "Cory Monteith, may your spirit be at peace, and may you fly with the angels... Heart-breaking, my prayers are with all of his loved ones!"
Taylor, 23, tweeted: "Speechless. And for the worst reason."
Demi Lovato, who has also been to rehab to battle depression in the past, wrote:
"#RIPCoryMonteith... So unbelievably tragic."
She added that her prayers are with Cory's girlfriend of one year and co-star Lea Michele, 26.
Kaley Cuoco, Olivia Munn and Kim Kardashian also expressed their sorrow after hearing the news.
The executive producers of 'Glee' released a joint statement to People.com, saying: "We are deeply saddened by this tragic news. 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."
His co-stars Dot Marie Jones and Damian McGinty admitted they are both devastated by the Canadian actor's death.
According to police, Cory, who checked into the hotel on July 6, was out with friends in the city on Friday night and returned to his 21st floor room in the early morning hours alone.
It was also said that he had been dead for several hours by the time his body was discovered by staff at the hotel, who went to his room after he missed his checkout time.