Sylvester Stallone is opening up about the pain of losing his son.

The actor, 80, recalled his son Sage dying at 36 due to coronary artery disease linked to atherosclerosis, resulting in a heart attack, in an interview with The New York Times published on Saturday, Sept. 26.

“The thing is, you have so many episodes of guilt. Like: What could I have done? Should I have been there? What if I did that? If I went right or went left?” Stallone said.

He recalled learning of his son’s death over an abrupt phone call.

“I’ll never forget, it was so cold: My mother’s new husband, who I’d never even met, who was a doctor, called me and goes: ‘Sly, he’s gone. Sage — he’s gone,’ ” he said. “I went, ‘Gone where?’ ‘He died, he’s gone. I’m sorry.’ Click.”

The Rocky star said that while he felt he was keeping it together in the following days, he became overcome with emotions about a week after his loss.

“Because of the funeral, dealing with the mother, dealing with your life in the present, it just takes you into a whole other world. You go: Wow, I’m holding it together. When’s it going to happen? And then about a week later, I was all alone in my room, and a wail came out of me I’ve never heard before or since,” the actor said.

“It was just pain and grief and guilt. It was not human,” he added.