The bedridden 79-year-old killer was being held at a high-secure hospital in Merseyside after torturing and killing five children with partner Myra Hindley.
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His death, hours after he was urged to "do the right thing" and reveal where the last of his child victims is buried, means he takes some of his secrets about the horrors to his grave.
Brady was jailed for the killings of John Kilbride, 12, 10-year-old Lesley Ann Downey and Edward Evans, 17, in 1966.
He went on to admit the murders of Pauline Reade, 16, and 12-year-old Keith Bennett.
Glasgow-born Brady had been held at Ashworth High Secure Hospital since 1985 and died at 6.03pm on Monday.
A spokesman said the serial killer, who used the name Ian Stewart-Brady before his death, had been on oxygen.
Brady was not found dead in his room in the Merseyside unit, the spokesman said, but he was unable to confirm if anyone was with him when he died, adding: "Quite possibly. I don't know."
Terry Kilbride, the brother of victim John, said he will still have to deal with the "nightmare" Brady has left behind.
He told the Sun: "It's a lot to take in. It's been years and years of anguish and pain for us and the families of the victims.
"But nothing will change. He's dead but we will have to still live with the nightmare that he left behind.
"He's ruined our lives all these years and he'll still ruin it even though he's gone. I feel numb."
Mr Kilbride added that there were no other words to describe Brady apart from "a murderous psychopath".
The crimes of Brady and Hindley - who died in prison in 2002 - shocked the nation as details of how the pair snatched children off the street, abused and tortured them to death were recalled during their trial at Chester Assizes.
Brady escaped the hangman's noose as the death penalty was abolished just months earlier and was handed three life sentences.
In 2013 Brady asked to be moved to a Scottish prison so he could not be force fed, as he could be in hospital, and where he could be allowed to die if he wishes.
His request was rejected after Ashworth medical experts said he had chronic mental illness and needed continued care in hospital.
In February he was refused permission to launch a High Court fight to have the lawyer of his choice representing him at a tribunal where the decision would be reviewed.
Former police officer Norman Brennan, who represented the family of victim Lesley Ann Downey, told Newsnight about the "grief and torment" he saw on the faces of her mother and father.
He told the programme: "To know that your daughter was lost, alone and murdered and then actually her death was recorded, the grief can never ever be etched from your mind.
"Those two individuals, Myra Hindley and Ian Brady, they didn't just destroy five young children's lives.
"For their relentless appeals and false hopes that they gave the families for over 50 years destroyed all of the families as well, even to this day."
The families of other victims of Brady have said his death has brought them closure.
Terry West, brother of Lesley Ann Downey, told MailOnline: "I poured myself a glass of wine when I found out - we've been waiting for this day for such a long time. It's closure for our family.
"But I really feel for Keith Bennett's brother Alan and the rest of his family - this probably means they'll never know where his body was buried.
"He's taken it to the grave. There's still one poor kiddie up there on the Moors. My heart goes out to Alan - at least I've got somewhere that I can visit our Les, he hasn't even got that."
Journalist Peter Gould, who had been in regular written contact with Brady since 1985, told BBC Breakfast there was only one instance where Brady appeared to express regret for his actions.
He said: "I have to say there was one occasion in the many letters he wrote to me over the years when he did express some kind of remorse. His phrase was 'my remorse is painfully deep'.
"That was the only occasion he really referred to the crimes he committed with Myra Hindley in those terms.
He added Brady was "probably tortured by the crimes he and Hindley had committed and could never really face up to them".
"That's why I think the impression has been created that he really showed no remorse at all", Mr Gould added.
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