Agca, 48, has already been given an advance of £280,000 by the unidentified film company which has secured the exclusive rights to tell his story and finally reveal his motivation, according to a report in an Italian news magazine.
The Pope was left fighting for his life after the Turkish gunman shot him twice as he greeted crowds in the Vatican's St Peter's Square in May 1981.
Details of the film deal emerged in an interview Haydar Mengi had given to the news weekly Gente.
Mr Mengi explained that Agca - who was released from an Istanbul jail last week - had gone into hiding to finalise the negotiations.
The bodyguard explained: "Agca has already received $500,000 as an advance on the $8 million deal.
"It was because of the negotiations that Agca went into hiding last week and did not sign on at his local police station as he should have.
"As part of the deal Agca must give a full interview about what happened leading up to the shooting and the shooting itself and he will also play himself in the movie. Other terms of the contract ban Agca from giving interviews and he must keep out of trouble."
Gente added that it was the temptation of the $8 million Hollywood offer that had led him to pull out of a $600,000 (£340,000) deal he had agreed for a television interview on his release.
Mr Mengi added: "The movie will be filmed in Mexico and Agca will fly out there shortly for the production.
"But Agca's life is without doubt at risk - he knows too much. Killing him is the only way of keeping him quiet.
"I'm certain he would be safe if he told his story to as many people as possible."
Agca was arrested immediately following the shooting and later sentenced to life in jail by an Italian court.
Two years later Pope John Paul visited him in his prison cell at Rome's Rebibbia prison, where the pontiff forgave him.
Six years ago, Agca was given a pardon by Carlo Azeglio Ciampi, Italy's president, and he returned to Turkey to serve an outstanding sentence for the murder of a Turkish newspaper editor.
Last week, a judge decided he had served enough time behind bars and he was released, although Turkey's justice minister has ordered a full investigation into his freedom and not ruled out him returning to jail.
Agca's motives for shooting the pope have never been properly explained: at first he claimed he had acted alone but then he said he had been hired by the Bulgarian secret service.
He later retracted that claim, but many are convinced that the assassination was ordered by the KGB in Moscow, who saw the Polish pope as a threat to communism in the Eastern Bloc.
Mustafa Demeribag, Agca's Istanbul-based lawyer, was unavailable for comment.
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