Paul Zimmerman / Retna Ltd. 1 / 8
Paul Zimmerman / Retna Ltd. 1 / 8

ET Online

Ahead of Thursday's "Glee" tribute episode, Cory Monteith's estranged father, Joe Monteith, spoke out about the grief he's endured since losing his son.

"It's just ripping my insides out and tearing me apart," Joe, 63, told People exclusively.

PICS: Remembering Cory

According to the news source, Joe last saw Cory two years ago after not seeing him for 11 years. As Joe wasn't consistently in Cory's life, he reportedly wasn't allowed to see his son's body before it was cremated.

While Joe wishes that he could've said goodbye to his son, he vividly remembers their last encounter, which involved a heart-to-heart about his split from Cory's mom.

Joe Monteith and Ann McGregor divorced in 1989. Joe claimed that his military job restricted him to seeing his family only once every six months. On top of that, Joe claims that Ann consciously kept Cory and his brother, Shaun, away from their father.

During their last face-to-face meeting, the father and son also spoke about Cory's addiction struggles and Cory reportedly promised his dad that he was clean.

"I lost my son," says Joe. "He should have known not to touch that drug again."