Glee took a deep, emotional toll on Ryan Murphy.
The executive producer of the Fox musical series opens up about the experience in a new interview, where he reveals the last time he saw star Cory Monteith, who tragically died of a drug overdose in 2013.
Murphy says that Monteith and his girlfriend at the time, Lea Michele, came to visit him on the set of HBO's The Normal Heart, where the late actor thanked him for helping push him through his struggles.
WATCH: Naya Rivera Opens Up About Battling Anorexia, Getting an Abortion in 'Sorry Not Sorry' Memoir
"We hugged, and the last thing he said was, 'I love you, man, and thank you for helping me get better,'" Murphy recalls to Entertainment Weekly. "And then the next thing I knew he was dead. It was like losing a child."
The Glee co-creator acknowledges the profound affect the actor's death had on the show.
“What started off as being such a great celebration of love and acceptance ultimately became about darkness and death,” he explained.
PICS: Remembering Cory Monteith
At times, Murphy reveals, the drama on the Glee set boiled over as the cast became too close.
"There was a lot of infighting," he says. "There was a lot of people sleeping together and breaking up ... We all got too personal."
MORE: Lea Michele & 'Glee' Cast Remember Cory Monteith on 3rd Anniversary of His Death
Even after all that's happened since Glee was introduced to the world in 2009, Murphy admits that the experience was "the best time in my life and the worst time in my life."
WATCH: Cory Monteith's First ET Interview