Former detective Mike Rothmiller has claimed in a new book that it was late US President John Kennedy’s brother Robert Kennedy, Attorney General of the US, also known as Bobby who killed Marilyn Monroe by giving the star drinks with spiked with drugs.

Rothmiller made the revelation in "Bombshell: The Night Bobby Kennedy Killed Marilyn Monroe,'' which will be out on July 8, reported The Sun. The book is co written by Douglas Thompson. 

Rothmiller found documents in Los Angeles Police Department (LAPD) archives that show that Monroe was murdered in 1962 to protect the Kennedy family. According to him, it was Bobby who gave Monroe the poisoned drink in the presence of actor Peter Lawford. When Rothmiller put the facts to Lawford, 20 years later, he broke down and confessed. 

The former cop kept quiet for decades as he feared for his life. He worked as an agent of the Organized Crime Intelligence Division (OCID) of the LAPD, had direct personal access to hundreds of secret files. He came across a copy of a document marked "Marilyn Monroe’s diary," reported Daily Mail.

On Aug. 3, 1962, the day before she died, she allegedly wrote, "Peter said Robert will come tomorrow. I don’t know if he will.’"

While going through the pages, Rothmiller saw Monroe considered Bobby as something much more than a casual boyfriend. He was married with seven children, but the Hollywood star seemed to believe that he was prepared to leave his wife, Ethel, and marry her.

A week before her death, Monroe made an entry in her diary, "Frank invited me to the lodge. He said it will be fun. He said never to mention Sam at the lodge. He’s Mafia." Frank was Sinatra, Sam was Giancana — head of the Chicago mob. 

The next entry read, "Frank, Peter and others were there. Frank said I can’t keep my f****** mouth shut. He told me to get out. I don’t know why he’s treating me this way. What happened to me? I was drunk. I don’t remember. Did I have sex?" Following that, her diary entries were angry. "They are not calling back. Bob and John used me. I told Peter they’re ignoring me. I’m not going to stand for that. I’m going to tell everyone about us."

Later, when the former cop met Lawford, he shared details of how Monroe died. He also narrated the horrific events at Sinatra’s lodge party where Lawford saw the singer was plying Marilyn with alcohol. She was carried, semi-conscious, into a back room where she was raped by Giancana. Then she was abused by a group of men and women. When Monroe woke up, Sinatra warned her to say nothing about her affairs with the Kennedys. But she couldn't be silenced by threats, sexual violence and blackmail.

According to Lawford, on Aug. 4, 1962 Bobby flew to Los Angeles. When Bobby told her to give her diary, Monroe lost her cool and started waving a kitchen knife. Lawford steered Bobby out of the house. But they came back in the evening, when Monroe looked hazy. Once again, their encounter got heated. "What do I want?" the actress yelled at Bobby. "What do I want? I don’t want to be treated like a f****** whore and ignored!" Bobby shook his fist in her face. She slapped it away. Holding her wrists, he swore in her face. She then slapped him after freeing herself. 

While Bobby searched the house for her diary, Lawford sat with her on the sofa in the living room, trying to calm her. Eventually, Bobby entered the kitchen. Lawford then went to plead with his friend to leave.  Bobby was stirring a glass of water with a spoon. He seemed to be pouring something into it. 

Monroe was crying when the two men went back into the living room. "Drink this, you’ll feel better," Bobby told her. Monroe drank and lay back. Now that she was quiet, both men searched the house, but couldn't find the diary. When they went back to the living room, the actress appeared to be sleeping. Bobby shook her shoulder until she stirred. Her voice was a whisper. Bobby said her name, but she didn’t respond.

Lawford shook her, but her complexion was turning waxen. "She’s not breathing," he said. "Leave her," Bobby said. They went to the door where they met two men. Lawford initially thought they were neighbors, later he realised they were detectives or secret service agents. Bobby nodded to the men, who then entered the house. Lawford knew Monroe was not merely "out of it." She was dead.

For the rest of his life, Bobby denied he had been in Los Angeles on the night Monroe died. Meanwhile, a LAPD search team found the diary, and got rid of the glass that Bobby gave Monroe.   

File picture of Marilyn Monroe Actress Marilyn Monroe poses for a portrait laying on the grass in 1954 in Palm Springs, California. Photo by Baron/Hulton Archive/Getty Images