Los Angeles, California (CNN) -- The copyright to a home movie of Marilyn Monroe "just sitting around" with friends will be offered through an online auction this week, according to a man who found the film while researching the actress' death.

A short clip of the four-minute, silent 16 mm film provided to CNN to shows Monroe puffing on a cigarette, laughing and drinking wine on a couch.

An FBI agent involved in the investigation of Monroe's death on August 5, 1962 -- which was ruled a suicide by drug overdose -- tipped off collector Keya Morgan to the film's existence.

Morgan was interviewing the agent for a documentary titled "Marilyn Monroe: Murder at 5th Helena Drive," he said.

The documentary, due out next year, examines the theory that Monroe was killed by government agents because of her affair with President John F. Kennedy.

Morgan said he paid $275,000 for the faded color film because it is "very rare" to find images of the actress' private moments.

"It's a side of Marilyn that no one has ever seen before," he said. "You see the private Norma Jeane, the girl. You don't see Marilyn Monroe, the movie star." Monroe changed her name from Norma Jeane Baker to Marilyn Monroe early in her acting and modeling career.

While she puffs the cigarette, "she's also sniffing her armpit and acting silly," Morgan said.

The woman who made the film asked that CNN use only her first name, Gretchen, to protect her identity.

"We were just getting together," Gretchen said. They were "just sitting around" in a New Jersey apartment, singing songs, she said.

The film was made in the late 1950s; Gretchen said she could not recall the exact year. She kept it packed away for 50 years, except for loaning it to FBI investigators, she said.

Gretchen retained the copyright, which Morgan is helping her sell through an eBay auction expected to begin Thursday, he said.

Very neat! I remember a few years ago a video surfaced of her walking down the streets of NYC, taken by a fan. He was a diehard fan of hers and he always made sure to see her whenever she came to New York, and one day Marilyn invited him to spend the day with her, and I think she took him out to dinner.

This is probably part of the footage...the YouTube video is titled "Marilyn Monroe smoking pot", although it just looks like a cigarette to me. Either way, nice footage.

Funny, I was just thinking about her death today...although it's not rare of me to be thinking about Marilyn.

Her death just doesn't add up. I've read so many books about the different theories on her death, and while there are many different theories and points of views, most people can agree on one conclusion: There was definitely a cover up. There are so many things that don't add up to the story that I can't even begin to mention...

I'ma say it was pot - the hooch dries your mouth out; the way she licks her lips, her tongue looks dry. Drymouth.

No one licks their lips like that when they smoke tobacco...Plus, dope was cheap and folks disguised it by rolling it fat, using "rolling machines" to pack regular cigarette-tubes (with filters) with pot, to mimic cigarettes...

Just speaking from "old school" experience.

Lovely, lovely woman.

She'd probably still be around today.

I had a friend who's Uncle (a Korean War Vet) used to smoke "Japanese Cigarettes." As we got older, we started to understand what Japanese Cigarettes actually were...... He also packed regular cigarette casings with the pot, so they looked like nothing out of the ordinary. The odor was never that of real cigarettes for some strange reason.... My friends mother always made him smoke his fags outside.

Thats just rude

She'd be in her eightees.........

Yep. 83.

Eternally in her 30's now.