Transcript for Private Eye's Files: 'I Listened to Marilyn Monroe Die'
startling details about marilyn monroe's final hours reveal the by a private eye's secret files and linsey davis is here with more. Reporter: Good morning. The documents we're talking about belonged to one of the most notorious private investigators that bugged marilyn monroe's house allegedly and was listening to everything happening privately in her final days. Fred otash was arguably the most famous hollywood detective it THE IN '50s AND '60s MAKING A Name for himself by spying on tinseltown's biggest stars. He was prepared to tape anyone for anyone. What he found was eye popping. Reporter: Otash died in 1992 but the hollywood reporter says it's now seen documents which may back up some of his most eye-popping claims including that he listened in on marilyn monroe in bed with president kennedy and allegedly eves dropped on an argument with his brother robert in the hours before her death. According to otash he overheard a violent argument between marilyn and robert f. Kennedy in which he claims she said popping around like a piece of meat and robert f. Kennedy got a pillow, put it over her head to keep her quiet. She calmed down and then he got out of there. Hours later, otash got a call saying that marilyn was dead. Reporter: Monroe's death was ruled a probable suicide from a drug overdose. In his notes he said I listened to marilyn monroe die. He didn't elaborate and kennedy has never been implicated or accused of wrongdoing. If he did hear a huge argument between her and bobby kennedy the day before she died, you have to wonder where the tapes are. Reporter: The lack of those recordings as well as other unsubstantiated claims led many in hollywood to brand him a con artist, but "the hollywood reporter" says after an unflattering portrayal in a new e-book otash's daughter is finally revealing his old files to help salvage his reputation. He was working for marilyn monroe while taping marilyn monroe so when you're a double agent like that you're not the most trustworthy guy around. Clearly otash knew something but he's not around to be interrogated. Reporter: After otash died his attorney allegedly wheeled a red file cabinet full of his most sensitive records out of his office never to be seen again. We should also note allegations about the kennedy's involvement with monroe have always been denied by those close to the family.
This transcript has been automatically generated and may not be 100% accurate.