On November 8, 1965, newspaper columnist and TV game show star Dorothy Kilgallen was found dead of an alleged drug overdose in her Manhattan townhouse.

Her death reportedly came just weeks before a trip she had planned to New Orleans to meet with a secret informant relating to an 18-month investigation she was conducting about John F Kennedy's assassination for a tell-all book.

A medical examiner at the time ruled her death accidental, caused by a combination of sleeping pills and alcohol, and the case was closed.

But lawyer and author Mark Shaw believes Kilgallen was the victim of foul play orchestrated by a mobster who feared her tell-all book would accuse him of being the mastermind behind Kennedy's assassination.

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Newspaper columnist and TV game show star Dorothy Kilgallen (pictured left and right) was found dead on November 8, 1965 of an alleged drug overdose in her Manhattan townhouse

Kilgallen (pictured far left) is best known for her role as a star panelist on CBS's TV game show What's My Line?

Now Shaw, author of The Reporter Who Knew Too Much, is calling for a full investigation into Kilgallen's death, charging that her death was a homicide and was covered up, and that the main suspect still remains at large.

'Murder is murder whether it happened five days or 50 years ago,' Shaw told the New York Post.

'Victims have rights, and Dorothy was denied hers because there was no investigation.'

Through the discovery of more than 40 videotaped interviews with some of Kilgallen's closest friends and one of the last people to see her alive - Shaw contends her death is a murder mystery featuring suspects including Frank Sinatra, Mafia Don Carlos Marcello and a 'mystery man' who may have silenced her.

In 1963, Kilgallen - best known for her role as a star panelist on CBS's TV game show What's My Line? - was devastated by Kennedy's November 22 assassination, according to Shaw.

Kennedy, who Shaw had considered a friend and even visited in the White House, was fatally shot by Lee Harvey Oswald as the then-U.S. president traveled through Dallas in a motorcade.

After his death, Kilgallen launched her investigation and dismissed the notion that Oswald acted alone, gathering evidence, including notes and interviews.

But after her death, the file of evidence was never found, with Shaw telling the Post that whoever silenced Kilgallen 'took that file and burned it.'

Author Mark Shaw believes Kilgallen was the victim of foul play orchestrated by a mobster who feared her tell-all book would accuse him of orchestrating the assassinations of John F Kennedy (left) and Lee Harvey Oswald (right)

Bystanders look on as Jacqueline Kennedy reaches over to help her husband and then-president who lies on the rear of a car after being struck by an assassin's bullet as his motorcade traveled through Dealey Plaza in Dallas, Texas in November 1963

Kilgallen died days before a trip to New Orleans where she was going to investigate Carlos Marcello (pictured) - who she had suspected of masterminding Kennedy's assassination

According to Shaw, Kilgallen was under surveillance at the time of her death due to her writings about Fidel Castro as well as Kennedy's assassination.

One of her hairdressers and close friend Charles Simpson said that Kilgallen had told him: 'If the wrong people knew what I know [about the JFK assassination], it would cost me my life.'

Kilgallen had reportedly also found an enemy with then-FBI Director J Edgar Hoover due to her Voice of Broadway columns for the New York Journal-America, criticizing Hoover and his theory that Oswald acted alone.

This caused Hoover to have a motive to silence Kilgallen, according to Shaw.

Kilgallen later managed to be the only reporter to interview Jack Ruby, the Dallas bar owner who fatally shot Oswald at Dallas police headquarters.

She later exposed Ruby's testimony to the Warren Commission before its official release, angering government officials.

As she researched Kennedy's assassination, intended for a tell-all book for Random House, she set up a second trip to New Orleans.

She was going to investigate Marcello - who she had suspected was the mastermind behind Kennedy's assassination.

Prior to her trip, she told a friend she was going to meet a source who she did not know, but said they were going to give her information about the case.

Kilgallen pictured center. In a letter set to be delivered to Manhattan District Attorney’s Office on Monday, Shaw writes that with the new evidence, 'investigating Kilgallen’s death is judicially responsible'

She also told her lawyer Mort Farber she was going to 'break the real story and have the biggest scoop of the century.'

However her tell-all book was never published after she was found dead ust days before the intended trip.

'The killers won, because she was eliminated and erased from any historical record about the JFK assassination,' Shaw told the Post.

When Kilgallen was found dead inside her Manhattan apartment, she was sitting up in a bed, dressed in only a blue bathrobe, and still had a floral hair accessory in her hair that she had worn the night before when she appeared on the TV game show.

An empty sleeping-pill bottle and a drinking glass were found on the nightstand, but Shaw contends they were part of a 'staged' death scene.

One of her hairdressers, Marc Sinclaire, noted that prior to her death Kilgallen had bought a gun and changed her will, adding she was 'scared for her life and family.'

He also said Kilgallen's body was found in a bedroom she never slept in and that she was wearing bed clothes she never wore to bed.

However, police at the time reportedly found nothing suspicious about the death, ruling out a suicide and homicide.

Mark Shaw, is calling for a full investigation into Kilgallen's death

An autopsy done at the time reportedly cited the cause of death as 'acute ethanol and barbiturate intoxication, circumstances undetermined.'

Joe Tonahill, who was Jack Ruby's co-counsel, said Kilgallen did not show any signs of being an alcoholic or using drugs prior to her death.

Never-before-released lab results from Killgallen's autopsy obtained by Shaw have revealed the presence of two other drugs in her system, tuinal and nembutal.

Shaw said three years after Kilgallen's death, two toxicologists found the extra drugs in lab tests but did not alert authorities.

Tests also revealed the glass found on the nightstand contained a powder residue, suggesting someone opened capsules and poured drugs into her drink, Shaw said.

Shaw also discovered her autopsy was conducted in Brooklyn Medical Examiner's and not the Manhattan office even though she died in Manhattan.

Dr Steven Goldner, who worked in the Brooklyn office, said that office was controlled by the mob and they 'deliberately sent her body to Brooklyn as part of the cover up,' according to the Post.

The last person to see Kilgallen alive, Katherine Stone, said she saw the journalist with a 'mystery man' talking 'serious business' at the Regency Hotel in New York City.

The mystery man was identified by Shaw as Ron Pataky, who was 12 years younger than her, who he believes Kilgallen had an affair with.

Kilgallen was married to Richard Kollmar, who she went on to have children with.

Shaw believes Pataky and Kilgallen's relationship fell apart when she started suspecting he was leaking her evidence about the assassination to her targets.

The Reporter Who Knew Too Much (cover of the book shown above) is out on December 6

Shaw contends that two poems written by Pataky 40 years after Kilgallen died suggest his involvement with the lines, 'Somebody who's dead could tell no tales,' and 'Make one of 'em poison' in a line about a bartender making drinks.

Pataky told Shaw last week that he 'loved Dorothy dearly' and denied an affair or that he was at the Regency Hotel the night before her death, according to the Post.

However, he did admit a close friendship with Kilgallen.

Through his findings, Shaw is hoping officials will fully investigate the Kilgallen case.

In a letter set to be delivered to Manhattan District Attorney’s Office on Monday, Shaw writes that with the new evidence, 'investigating Kilgallen’s death is judicially responsible.'

'Even though the events surrounding her death are now five decades old, I do not believe your office’s re-opening the investigation will result in futile posturing,' he wrote.

'There are strong leads based on credible witnesses and a primary suspect is indeed still alive.'