Profile of a killer: Alesha MacPhail murderer filmed himself on video game featuring news report about the killing of six-year-old girl

Aaron Campbell was fixated on violent computer games from an early age.

The 16-year-old lived an almost nocturnal existence, alone in his bedroom playing on his computer through the night. The darker, more violent the games, the better.

During the police investigation into Alesha’s murder, videos of Campbell playing the chilling games were found by detectives.

In one clip, the then 12-year-old gave a running commentary as he explored a creepy house, where walls were spattered with blood and gore. He also filmed himself playing a game that featured a fictional news report about the slaughter of a six-year-old girl.

The 15-minute footage shows Campbell, then 14, at the controls of an adult-themed game. The homemade clips provided police with an insight into the mind of a youth hooked on gory and bloody images.

Police officers also discovered Campbell had an obsession with horror character Slender Man. In an echo of the teenager’s real-life atrocity, the movie villain kidnaps and traumatises youngsters.

The character has already been linked to a murder when it was the motivation for the horrific stabbing of a schoolgirl by two 12-year-olds in the US in 2014.

Eighteen months before Alesha’s murder, Campbell told a friend he “might kill one day for the lifetime experience”. But no one realised just how dangerous Campbell was.

His mother Janette admitted he was addicted to gaming. The 54-year-old said: “He would lock himself away until 2am on Fridays and Saturdays. He’d be up all night on the computer and sleep all day.”

Knives, drink and drugs came into his life in his early teens. He was 14 when he started buying cannabis regularly from, among others, Alesha’s father Robert.

Ironically, the Campbell family had moved to Bute from England in the hope of finding a safer place to raise their kids.

But despite being a promising pupil, there were warning signs – a lack of empathy, rumours of skinning cats, an interest in voodoo. One neighbour claimed he had been caught trying to set fire to buildings.

One local in his home town of Rothesay said: “If you caught his eye, he would stare right back at you and hold your gaze.”

That same stare was on the killer’s face as Alesha’s granny Angela King gave evidence about the “beautiful, happy girl” she had lost. And it was back again last Thursday when the jury returned their guilty verdict.

The trial heard how Campbell had gone to Alesha’s dad’s house in Rothesay just before 2am, on July 2, to buy drugs. Alesha was asleep in bed.

After phoning Robert, Campbell had set off for MacPhail’s home, from where he snatched Alesha, raped and murdered her, inflicting more than 117 separate injuries. After the verdict, Lord Matthews, said he had carried out “some of the most evil and wicked crimes.”

He will be sentenced next month.