Despite Brady's death, Greater Manchester Police said Tuesday they won't close the case of Bennett's murder and would act on "credible and actionable" information in the search to find the boy's body.
After half a century behind bars, the Moors Murderer, who sexually assaulted, tortured and murdered several children and young people.
Brady, who revealed he had a lung and chest condition in December, had been receiving palliative care from cancer nurses at Ashworth psychiatric hospital on Merseyside.
"We can confirm a 79-year-old patient in long term care at Ashworth High Secure Hospital has died after becoming physically unwell", the service said.
Lawyers representing Brady had announced in February that he had been bed-ridden for years and it was "fair to say" that he was terminally ill.
In a statement, Greater Manchester Police said it is not actively searching Saddleworth Moor but would never close Keith Bennett's case.
Mr Makin, the executor of Brady's will, said he was called to go and see the murderer hours before his death at 6.03pm on Monday.
Hindley died in prison in 2002, aged 60.
In 2013, a Mental Health Tribunal rejected his request to return to prison, ruling it was necessary in his interests and for the safety of others that he remain at Ashworth.
The body of the third victim, Keith Bennett, 12, has never been found.
Keith's mother, Winnie Johnson, had repeatedly pleaded with Brady to say where he disposed of the body before her own death in 2012.
Brady escaped the hangman's noose as the death penalty was abolished just months earlier.
Coroner: Killer Brady's ashes mustn't be scattered on moor
John Kilbride's brother, Terry, told the Sun newspaper: "It's been years and years of anguish and pain for us and the families of the victims".
Killer couple Myra Hindley and Ian Brady.
Police and government officials are hoping the coded letters will help them find the body of 11-year-old Keith Bennett, from Manchester, who went missing in June 1964.
The boy's remains have never been found despite widespread searches on Saddleworth Moor, near Oldham in Greater Manchester.
"I don't think useful information is going to come from him".
"Good riddance that he's gone, I don't drink but I will have a pint".
Conceding that he did not have the legal power to withhold the body he said the decision was the "right and proper moral judgment to make" as it would be "offensive" if they were.
Alas, however, he departed this earth with one final insult to the families of those he murdered, and kept the location he buried 12 year old Keith Bennett a closely guarded secret in his sadistic game of cat and mouse, and upon his death essentially gave the family the middle finger by not divulging the information.
Ten-year-old Lesley Ann Downey could be heard whimpering: "I want to see my mummy".
Scotland's First Minister Nicola Sturgeon said: "I don't think anybody will mourn Ian Brady".
It was there that he met Hindley and it is said she fell completely under his influence.
He and his lover, Myra Hindley, were convicted and sentenced to life in 1966 for the murders of Lesley Ann Downey, 10, and Edward Evans, 17.