Why Frank Sinatra Believed Marilyn Monroe Was Murdered: A New Book Reveals

Tony Oppedisano's memoir Sinatra and Me: In The Wee Small Hours is excerpted in this week's PEOPLE

Marilyn Monroe and fFank sinatra. Photo: Moviestore/Shutterstock

In the later years of his life, Frank Sinatra would often reminisce about his loves, his losses and the friends he missed most, including Marilyn Monroe.

While the events surrounding what really happened on August 4, 1962 when the star was found dead from a drug overdose remain a mystery, Sinatra's close confidant and former road manager Tony Oppedisano, whose memoir Sinatra and Me: In The Wee Small Hours, is excerpted in this week's PEOPLE, says the singer didn't believe it was an accidental overdose. "Frank believed she was murdered," he writes, "and he never got over it."

According to Oppedisano, Sinatra and Monroe were close friends but not lovers. While Sinatra thought she was beautiful and funny, he writes, "Frank felt she was too troubled, too fragile, for him to sleep with and then walk away."

She did however confide her most intimate secrets including her affairs with John F. Kennedy and Robert F. Kennedy.

When the affairs ended abruptly, he continues, "Marilyn told Frank she didn't understand why they'd shut her out completely once she stopped having sex with them."

The weekend before her death, the actress spent time at the famous Cal Neva Lodge, outside of Lake Tahoe, partially owned by Sinatra.

What the world didn't know, the author reveals, was that she was there to spend time with her ex-husband Joe DiMaggio who was staying nearby and that she had decided to make a press announcement the following week that they were getting back together.

From left: Robert F. Kennedy, Marilyn Monroe, and John F. Kennedy. Cefcil Stoughton/The Life Picture Collection/Getty

The news of a press conference sparked a rumor that Monroe was going to share details of her relationships with JFK and RFK. But, Oppedisano writes, "Frank said she'd never have spilled about the Kennedys because she still had feelings for [Jack.]"

And he says, "Frank believed if the press conference hadn't been announced, she would have lived a lot longer."

Within days of Monroe's death, he writes, Sinatra's attorney Mickey Rudin, who also worked with Monroe, told him that the actress had been killed. It was a rumor also circulating among Mob Boss Sam Giancana's men, some of whom claimed involvement. According to the book, Sinatra had several sources who told him the same story: "She'd been murdered with a Nembutal suppository and Robert Kennedy or the Mob was involved."

Over five decades later, the truth remains a mystery. "Conspiracy theories abound and I can't lay them to rest," writes Oppedisano. What he does know, is that Sinatra remained haunted by her death.

She was one of the many friends, including his Rat Pack pals Sammy Davis Jr. and Dean Martin, whom he reminisced about in his later years when they talked, often until dawn, at the singer's beloved Palm Springs compound. The stories were long held private but now 23 years after Sinatra's death, Oppedisano hopes by sharing them, he can show the human side of the music icon.

"I tried to paint the portrait of a man very few people got to know as well as I did," he says fondly. "I think he knew someday I'd share the stories he wanted the world to know."

For more on Frank Sinatra and the secrets he held close, pick up a copy of this week's PEOPLE.