What was supposed to be a weekend celebration of the musical TV series "Glee" turned into an impromptu memorial of song and dance for Cory Monteith after news of the "Glee" co-star's death rocked a "Glee" fan convention in England.

The hundreds of "gleeks," as they're known - joined a chorus of thousands worldwide who took to social media with similar expressions about Monteith's passing. The actor's struggles with addiction echoed those of other young stars whose premature deaths also left young fans grieving.

"The whole day was simultaneously the best and worst experience of my life," said Chloe Harvey, an 18-year-old fan from Portsmouth, England. "The news was devastating. No one had any idea what to say or do. It just shows how much of a truly amazing guy Cory was that everyone was so shocked and emotional about the news. Everyone was crying and sharing their stories."

Monteith, 31, was found dead in his Vancouver, British Columbia, hotel room on Saturday, according to police, who said an autopsy is expected Monday to determine the cause of death.

Police said Monteith had been out with people earlier, but video and electronic records from the hotel indicated he returned to his room by himself early Saturday morning. He was believed to be alone when he died.

The Fox network and the producers of "Glee," including 20th Century Fox Television, called Monteith an exceptional performer "and an even more exceptional person." They said he was "a true joy to work with and we will all miss him tremendously." Lea Michele, Monteith's "Glee" co-star and real-life girlfriend, asked for privacy upon hearing the news of his death.

While it's not known what caused his death, Monteith's passing recalls the lives of Heath Ledger, Corey Haim and River Phoenix - actors who battled substance abuse and died in their 20s and 30s. Monteith talked bluntly about struggling with addiction since he was a teenager, calling it a serious problem and telling Parade magazine in 2011 he was "lucky to be alive."

Monteith admitted himself to a treatment facility in April for substance addiction and asked for privacy as he took steps toward recovery, a representative said at the time. Michele told People magazine that she loved and supported him and was proud he was seeking help. It was not Monteith's first time in rehab. He also received treatment when he was 19.

"I think kids really need a place to go and feel like they belong," he said in the video posted the site for Project Limelight, a Vancouver charity offering theater and arts programs to at-risk youth. "When I was a kid, I struggled a lot with who I was and where my life was going and what I was interested in. And I was fortunate to have the arts inspire me."

Monteith similarly moved fans. At the weekend "Glee" convention, instead of planned revelry like singing competitions and autograph sessions with actors who've played members of the rival Warblers glee club, organizers Starfury Conventions rescheduled the final day of the three-day event at Heathrow's Thistle Hotel so the 250 attendees could mourn him together.

"We all woke up to hear the story, and no one really wanted to believe it was true," said Chloe-Louise Bond, a 22-year-old fan from Wakefield, England. "Walking into the main room, you could just feel the tragedy in the air, absolute strangers became a family right in that moment. Everyone was crying and hugging and just trying to get over the shock."

It was a day filled with sadness and songs. The attendees chanted "Cory! Cory! Cory!" In unison, they sang tunes like "Don't Stop Believin'," the Journey cover crooned by Monteith in the high school-set musical's first episode. Curt Mega, Telly Leung and other actors who've played Warblers led a group discussion with fans about their memories of Monteith.

"Glee," with its catchy song-and-dance numbers and high-profile guest stars like Gwyneth Paltrow and Britney Spears, became an instant hit when it debuted in 2009 and made celebrities of Montieth and the rest of the relatively unknown cast. Over the past four seasons, he delivered renditions of such classics as U2's "One" and R.E.M.'s "Losing My Religion."

Monteith served as the show's resident hunk with a heart of gold. He played Finn Hudson, a football quarterback with two left feet who found more camaraderie in the choir room than on the football field. After his character graduated high school, Hudson sought out to find himself before settling on what he wanted to do with his life: become a teacher and mentor.

Outside the Vancouver hotel where Monteith's body was discovered, a makeshift memorial popped up where fans left flowers and notes commemorating the actor. (hash)RipCoryMonteith and (hash)StayStrongLea became trending topics on Twitter.