Cory Monteith's death shook the 'Glee' cast and crew to their core. The tribute episode to the star, who died of a lethal mixture of heroin and alcohol, will air this week. Titled 'The Quarterback,' it was the absolute hardest episode anyone on cast or crew has ever had to shoot.

"People are still not over it. It is still really difficult," 'Glee' creator Ryan Murphy admitted to PEOPLE. "I've never seen a crew that can't continue shooting because they left the room sobbing. ... What you're seeing is what they felt not just about Finn, but Cory." He added, "It was very rough with Lea [Michele]."

Michele's heartbroken vocal cover of Bob Dylan's 'Make You Feel My Love' plays in the promo clip for the tribute, which features the cast paying their own in-show tributes to Finn Hudson, many of them (including Michele and Chris Colfer) crying real tears.

"I think the performances are quite stunning," Murphy said. "Honestly, almost everything from that episode is from the first take – of every performance – because the actors and the crew had a really hard time shooting it. … But I am very proud."