Those who knew, loved and were fans of Cory Monteith are struggling to make sense out of his tragic passing in a Vancouver hotel room Saturday. “Glee” co-star Mike O’Malley shared his memories of the 31-year-old actor with People on Monday.

O’Malley, who plays Burt Hummel, Monteith’s character Finn’s stepfather on the hit Fox show, said he and the rest of the “Glee” cast were “rocked” by the sudden death. "Cory Monteith was a great guy: funny, deep, thoughtful and hardworking," O'Malley told People Monday. "In real life, he was the coolest dude, generous, and a great friend to his pals."

"If an ability to show others kindness and fostering fellowship are two qualities that all humans should strive for, Cory mastered them long before he died. He deserved a long life. His death has rocked all of us at 'Glee.'"

"As Finn Hudson, he did what so many actors strive to do: authentically portray human behavior in a specific, understated manner, thereby eliciting laughter and creating camaraderie with his audience," O'Malley told the magazine.

Other colleagues are equally grief-stricken. Naya Rivera, who plays Santana on the show, told The Hollywood Reporter, "The entire ‘Glee’ family and I are deeply saddened by this tragedy. Cory was and always will be a part of my own family and a good friend. My heart goes out to Cory's family and Lea [Michele]."

Though he struggled with substance abuse, Monteith was said to have been doing better. According to People, Maureen Webb, who is the co-founder of a charity close to Monteith, Project Limelight Society, said he had "a quiet night with a lot of laughing" two days before he turned up dead.

"He looked so good, so healthy," Webb said. "I hadn't seen him look that good in a long time."

It hasn’t been determined what led to his death, but Monteith’s autopsy is expected to be released in two to three days. It’s widely suspected that drugs or alcohol might have played a role.