A woman told gardai that she saw the late paedophile Eamon Cooke kill schoolboy Philip Cairns at his radio studios in Inchicore in the 1980s.
Philip Cairns vanished without a trace as he walked back to his school, Colaiste Eanna in Rathfarnham, on October 23, 1986.
Now, incredibly, almost 30 years later, a woman has come forward with fresh information to claim she saw a disagreement between the pair.
She told detectives that she was at the radio studio and saw Cooke strike the schoolboy with an implement.
When she went into the room, she saw the 13-year-old boy bleeding and unconscious. She passed out shortly afterwards.
It's understood that the woman told this to gardai in Terenure in May.
Cooke (79), a pirate radio DJ who was found guilty of 42 counts of sexual abuse in 2007, died last week.
Gardai interviewed Cooke in the weeks before his death, at a hospice where he was being treated following temporary release from Arbour Hill prison.
It is understood Cooke admitted to meeting the schoolboy at his radio studios and corroborated some aspects of the woman's story.
"It took an awful lot of courage for this person to come forward," a source said.
Gardai are closely examining the DNA left on Philip's schoolbag, which was found in a laneway a few days after he disappeared.
It is understood three DNA profiles have been obtained from the schoolbag.
Gardai interviewed Cooke twice in the weeks before he died, giving him a number of opportunities to tell them exactly what happened and where Philip's body was.
However, it is believed Cooke would not give this information.
It is not known how the woman knew Cooke.
At this stage, gardai are not willing to say that the mystery of Philip's disappearance almost 30 years ago has been solved.
However, they are treating the woman's story as credible.
Philip's family have been kept informed of the recent developments.
"At this point in time these new lines of inquiry have not yielded positive results. However, the investigation is very much active and ongoing," a garda spokesman said.
Last night, Dublin TD John Lahart, who grew up in the area, said that Philip's disappearance "shocked, dazed and bewildered the community".
"The news tonight will be met with a mixture of terrible shock and confirmation of a community's worst fears, even after all this time," he told the Herald.
"His mother, Alice, and his late father, Philip Snr, carried the burden of his disappearance during the passing years with such great dignity, stoicism and grace," he said. Philip's father died in 2014.
"We can only hope that they will succeed in finding the final pieces of this puzzle and provide closure for a devastated family."
During his 2007 trial, the court heard his terrified young victims dubbed the DJ the 'Cookie Monster'. He was sentenced to 10 years in prison.