Twisted killer Nicholas Prosper chillingly outlined his murderous intent in a 70-second video recorded just hours before the massacre.
Wearing a yellow bucket hat and a black T-shirt, the teenage fantasist calmly and dispassionately said he would take violent revenge against his 13-year-old sister Giselle over her actions in a computer game.
The video was one of several files posted online in which Prosper, 19, spewed his sick views, often signalling his obsession with children.
His disturbed ramblings were so depraved that he was kicked off a gore website – where millions of users share and comment on videos of people being killed – because of his warped stance on child abuse. Prosper’s content was uploaded under a pseudonym and featured his distinctive accent.
His videos have been deleted from YouTube in the wake of his appalling crimes, although the Mail has been able to view them. They include a clip recorded hours before the massacre, believed to be filmed in his family’s flat in Luton.
Prosper said: ‘On June 30, my sister decided to make the incorrect choices on episode one of season one of The Walking Dead games, and for that her face will be mutilated further than necessary.’
Prosper said he was ‘chosen’ to protect a fictional character called Clementine in the zombie video game, in a sign he struggled to differentiate between the real world and make-believe.
Killer Nicholas Prosper threatened violent revenge against his 13-year-old sister Giselle over her actions on a computer game
Left to right: Giselle Prosper, 13, Juliana Prosper, 48 and 16-year-old Kyle Prosper were all killed in their own home
The three casualties were found in the Leabank area of Luton on September 13 last year – before their killer Nicholas Prosper, then 18, was arrested nearby
The teenager spent so much time on the internet in his bedroom that neighbours had no idea he even existed – despite them being on friendly terms with his mother and siblings.
One woman told the Mail: ‘I’ve lived here for 15 years and I never saw him once. Juliana and the other kids I saw, usually by the lifts.
‘She would often say hello and chat, she was so nice. I saw all the other siblings but never Nicholas – ever. One lady who lives on their floor said she never knew he even existed.’
Prosper peppered online forums with his repulsive ideas, many relating to children and including the sexual abuse of dead bodies. His rants were so revolting he was banned from a gore website for repeatedly ‘sexualising minors’.
One moderator told the Mail: ‘There were multiple comments by him either in support of or arguing for child-adult sexual interactions that made it clear this was not in jest or a careless attempt to play devil’s advocate.
Prosper said he was ‘chosen’ to protect a fictional character called Clementine in zombie video game The Walking Dead, in a sign he struggled to differentiate between the real world and make-believe
Nicholas Prosper today admitted the murders of his family members (pictured left to right) Kyle, Juliana and Giselle
Nicholas Prosper (pictured), 19, had previously denied murder but he dramatically entered guilty pleas during a six-minute hearing at Luton Crown Court this afternoon
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‘We do not know what sort of person Mr Prosper was, other than someone unwilling or incapable of following our site’s rules and therefore someone we would not allow on our platform.’
In another video, Prosper sarcastically suggested that child sexual abuse was blamed for ‘virtually every mental disorder and issue’.
Apologising for his ‘slurred’ speech, the teenager said: ‘Who knows, maybe in a few years we’ll see Aids, rectal cancer, increased chance of stubbing your toe, every single problem you face in life is because you touched a winky [penis] when you were six.’
Prosper also said disorder across the UK prompted by Axel Rudakubana’s triple murder at a Taylor Swift dance class last summer was ‘beneficial’ to Sir Keir Starmer.
