Glen Campbell was a legend who changed the face of country music. But behind the glitz and glamour was a man that had his own share of struggles. In her upcoming book, his widow, Kim, details the night Campbell pointed a gun at her in an alcohol-fueled rage.

In the new memoir Gentle On My Mind: In Sickness and in Health With Glen Campbell, Campbell’s wife of more than three decades recounts the days in which Campbell battled both drug and alcohol addiction.

"When he wasn’t drinking, he was the best guy in the world," Kim says in a new interview with People magazine about her book, which details her 34-year marriage to the “Rhinestone Cowboy" singer.

“But I feared every time he took a drink. I used to tremble, physically shake all over because it had gotten so bad."

One of the worst moments came just after the birth of their first son Cal in 1983, when Campbell had drank himself into an all-out fury.

"He got hold of the bottles I’d put in the linen closet and drank himself into another crazed rage,” Kim writes in a published excerpt from the revealing book. “This one was bad. This one had him pointing a pistol at me. He leveled the gun at me as if he were lining up a target. I froze. Then, without a word, he turned and walked the other way. I was scared to death. I felt so stupid for having had a baby with an alcoholic. Now our very lives were at risk."

In the book, Kim also looks back on those painful years in which Campbell battled Alzheimer’s Disease, which ultimately took his life in August of 2017.

"The unique thing about Alzheimer's is that you lose them twice," Kim says. "You lose them when they lose their memory and then you lose them physically. So I was grieving for many, many years. As more time goes on, it's getting easier. But there’s an empty spot that no one can ever fill, and it's never going to go away."

Gentle On My Mind: In Sickness and in Health With Glen Campbell is set for release on June 23.

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