"His last words to me were, 'I want to get better,' and I always felt and continue to feel even in his death that he did, that he really wanted to fight it and he was humiliated and shamed," Murphy told E! News.
The conversation took place in mid-June, when Monteith voiced his fears that he would be fired from the TV series that made him a star.
"We reassured him that the only thing that mattered was him getting better and his job was 100 percent protected because he thought he was going to get fired. That has been feeding into all of this, why it's so shocking and so debilitating and tragically sad because we were all rooting for him and trying to help him in every way that we could," Murphy added, while revealing he'd wanted Monteith to remain in rehab longer or at least move into an assisted sober living situation for a time.
The producer also revealed that Monteith's character of Finn will be killed off in the show's third episode after Glee returns September 26.
Production will then shut down for an "extended hiatus," Murphy said while he and his team and the cast, especially Cory's on and off-screen love, Lea Michele, figure out what to do next.