Twisted Killer Nicholas Prosper outlined her murderous intention in a video of 70 seconds that was only taken for a few hours before the massacre.
The teenage pasist wore a yellow bucket hat and a black T-shirt and said calmly and damping that he would take violent revenge against his 13-year-old sister Giselle about her actions in a computer game.
The video was one of the many online files in which Prosper, 19, spit on his sick views, often pointing to his obsession with children.
His disturbed walks were so corrupt that he was kicked off a GORE website – where millions of users share videos and comment on people who are murdered – because of his crooked position on child abuse. The content of Prosper was uploaded under a pseudonym and contained its distinctive accent.
His videos were removed from YouTube after his terrible crimes, although the post was able to view them. They contain a clip admitted hours before the massacre, which is assumed to be filmed in the flat of his family in Luton.
Prosper said: “On 30 June my sister decided to make the incorrect choices on episode one of the season one of the walking dead games, and for that her face will be mutilated further than necessary.”
Prosper said that he was 'chosen' to protect a fictional character called Clementine in the Zombie video game, in a plate he had difficulty making a distinction between the real world and the conviction.
The teenager spent so much time on the internet in his bedroom that neighbors had no idea that he even existed – even though they were on friendly conditions with his mother and brothers and sisters.
Killer Nicholas Prosper Endried violent revenge on his 13-year-old sister Giselle about her actions on a computer game
From left to right: Giselle Prosper, 13, Juliana Prosper, 48 and 16-year-old Kyle Prosper were all killed in their own house
A woman told the mail: 'I lived here for 15 years and I have never seen him. Juliana and the other children I saw, usually at the lifts.
“She would often say hello and chat, she was so nice. I saw all the other brothers and sisters never Nicholas – ever. A lady who lives on their floor said she never knew he even existed. '
Prosper peppered online forums with its disgusting ideas, many with regard to children and including sexual abuse of dead bodies. His tirades were so rebellion that he was banned from a GORE website for repeated 'sexualizing minors'.
One moderator told the mail: 'There were several comments by him in support or arguing for sexual interactions of children who made it clear that this was not joking or a careless attempt to play the devil's lawyer.
Prosper said that he was 'chosen' to protect a fictional character called Clementine in Zombie Video Game The Walking Dead, in a plate that he had trouble making a distinction between the real world and the conviction
“We do not know what kind of person Mr. Prosper was, except that someone who was not prepared or unable to follow the rules of our site and therefore someone we would not allow on our platform.”
In another video, Prosper Sarcastic suggested that the sexual abuse of children was blamed for 'almost every psychological disorder and issue'.
The teenager apologized for his' unclear 'speech and said:' Who knows, maybe in a few years we will see AIDS, rectum cancer, an increased chance of punching your toe, every problem with which you are confronted with in life, because because because you have touched a wink [penis] When you were six. '
Prosper also said that disorder in the United Kingdom was inspired by the triple murder of Axel Rudakubana during a Taylor Swift dance lesson last summer was 'useful' for Sir Keir Starmer.
