The disturbing internet history of a triple killer

Nicholas Prosper posted a video alluding to an apparent obsession with a child video game character

When police officers stopped 18-year-old Nicholas Prosper in Luton one Friday morning last September, he had already killed his mother, brother and sister and was planning to commit a mass shooting at his old primary school. So who is he, what do we know about his background and what questions remain unanswered?

Prosper lived in a council flat with his mum Juliana and two of his younger siblings, Kyle and Giselle, on Luton's Marsh Farm estate.

Warning: This story contains distressing details

Juliana Falcon, 48; Kyle Prosper, 16, and Giselle Prosper, 13, were found dead at their home in Luton in September

Police were called to reports of a disturbance at a flat in Leabank on Luton's Marsh Farm estate

In the early hours of Friday, 13 September, Prosper shot them all dead. An inquest heard they each had gunshot wounds to the head.

Police, responding to reports of a disturbance, apprehended him, before finding a loaded shotgun and more than 30 cartridges in a bush.

At Prosper's first court hearing, his father Ray Prosper shouted: "I still love you, son. It's not your fault, OK?" and then wept.

On Monday, Prosper pleaded guilty to the murders. Police have since confirmed he intended to carry out an attack at St Joseph's Catholic Primary School in Luton.

Floral tributes were laid following the discovery of the bodies of Prosper's mother, brother and sister

Prosper had no history with the local mental health trust.

Few details were released in the 10-minute court hearing, but Prosper's internet history - analysed by the BBC - paints a troubling picture.

One website he seemed to be a frequent user of featured videos of people's final moments.

Eerily, he also appeared to have an interest in mass shootings, including the 1999 Columbine High School massacre.

He was banned from that website after making comments of a pro-paedophile nature, and even admitted to having watched a notorious child sexual abuse video.

However, has not been charged in relation to possessing any such material.

Nicholas Prosper had planned a mass shooting at his former primary school

Perhaps even more disturbing was Prosper's apparent growing obsession with a child character called Clementine from The Walking Dead video game.

In a video posted after the killings, he told the camera: "I am the chosen one; chosen by Clementine. I am guided as Christians are guided by Jesus Christ."

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Both Prosper and his brother Kyle had attended Cardinal Newman Catholic School, which described Kyle as a "much-loved former student... known for his kindness and for simply being 'a brilliant friend' to so many of his fellow students".

In light of revelations that Prosper had been planning a mass shooting, it said it wanted to "reassure our community that the safety, wellbeing and happiness of the students and staff at our school will always be our number one priority, and this will never be compromised".

It added: "Security at the school is constantly reviewed and monitored, and that gives us the assurance that the measures we have in place are robust and effective."

It is not known whether there were any behavioural concerns about Prosper; whether he received any additional support or whether he was on an education, health and care plan.

Nicholas Prosper will be sentenced next week

Hazel Simmons, Labour leader of Luton Borough Council, said: "When we heard the revelation that he planned to cause further harm after the terrible murders [there] was shock, upset, concern."

She said she had received emails from some concerned parents of St Joseph's pupils.

"Obviously I can't underestimate how the parents and the school must be feeling at the moment and I can assure them we will do all we can to work with them around the security at the school and any other help that they need at this time," she said.

Ms Simmons added that she did not know whether the family were known by the council to have problems.

Schools across Luton had already been asked to review security after a fatal knife attack at a school in Sheffield, but the council has asked them to conduct a further review in the wake of Prosper's admissions.

Prosper will be sentenced over the course of two days next week, during which many more details will be made public.

What is already clear is that his actions have torn a family apart.

Bedfordshire Police's Det Ch Insp Sam Khanna said: "This was a truly tragic and shocking case in which three innocent members of the same family have been brutally killed by their son and brother."