A boy who was arrested for two murders and a rape before reaching his 16th birthday was facing life in jail today.
Nathan Harris was convicted of ordering the execution of young father Craig Brown as he unloaded Christmas shopping.
The officer leading the investigation said Harris had a "violent tendency" and it was "exceptional" for such a young person to be involved in such a serious crime.
Video footage posted on YouTube and handwritten rap lyrics found in his bedroom showed the teenager's obsession with guns and violence.
Text messages on his mobile phone appeared to show other youths asking him to procure firearms for them.
Harris had first come to the attention of police when he was just 13 years old following the murder of 16-year-old Kodjo Yenga in March 2007.
He was one of a number of teenagers rounded up by detectives for questioning, although he was never charged with the crime.
In December 2007 when he was 14, Harris was alleged to have taken part, with another youth, in the rape of a teenage girl, but was formally cleared following a trial at Inner London Crown Court.
Mr Brown, 20, was shot five times outside the home of his girlfriend Denica Date in Shepherd's Bush, west London, on Christmas Eve last year, following a series of mobile phone calls started by the youth.
Miss Date would later identify him as being at the scene of the shooting after seeing his picture on social networking site Facebook, the Old Bailey heard.
Harris had set in place the "lethal train of events" that led to the murder after seeing Mr Brown - who he believed to have "dissed" a friend - in the area.
Detective Inspector Kenny McDonald said: "He has got a violent tendency."
He said of Harris's involvement in crime at such a young age: "It is surprising, it is quite shocking really.
"It is still rare but we are mindful that people of Harris's age do seem to be finding an attraction with gangs and guns and knives.
"It is worrying and we as a society need to try and address this because we shouldn't be having people of his age having access to firearms.
"There are lots of terrific young people in London not involved in this, doing the right things, staying out of trouble. He is an exception."
Harris received his first conviction at the age of 13, for attempted robbery, and four months later was in court again for obstructing a drugs search. He was given referral orders for both matters.
In November last year, at the age of 15, he was given a conditional discharge for cannabis possession.
The boy, who went by the street name "Money" was just 15 at the time of his arrest for Mr Brown's murder, yet when police investigated his mobile phone they found text messages suggesting an involvement with firearms.
There were references to "45" and "star nine" handguns as well as requests for "no bodies" weapons - meaning those not linked to previous crimes.
Pages of handwritten rap lyrics contained references to stabbing and shooting, as well as a gang called IOC - "Instruments of Cruelty" or "Intelligence over Cops".
One document entitled "I.O.C. Christmas" had lyrics about using guns such as "we will cock it bk den squeeze".
Lyrics transcribed from his YouTube appearance read: "Mumsy kinda grumpy yeah she caught me in my room, me Shack and Dirty loading the pumpy."
He was today convicted of Mr Brown's murder while Adil Saed, 21, of Shepherd's Bush, Khalid Elsheikh, 22, of Hammersmith, west London, and a 17-year-old youth, who cannot be named, were cleared of the charge.
Elsheikh was, however, found guilty of a separate charge of possessing a firearm with intent to endanger life.
Judge Richard Hawkins lifted reporting restrictions preventing the naming of Harris and remanded both he and Elsheikh in custody for sentence next week.
The court heard that Mr Brown was gunned down by two men as he took wrapping paper out of his car boot following a day out with his girlfriend and their four-year-old son.
Mr Brown, a drug dealer from Battersea, south London, had been involved in a fight with Elsheikh during the summer.
In the months following the confrontation, his visits to the area to see his girlfriend became less frequent, jurors were told.
But when Harris spotted Mr Brown in the area last December he alerted other youths in a series of mobile phone calls, said Aftab Jafferjee QC, prosecuting.
"What Harris did was effectively to set off a lethal train of events quite deliberately," said Mr Jafferjee.
"Revenge was going to be as swift as it was brutal. In less than 35 minutes Craig Brown was shot dead outside Denica's house. Those responsible had swift access to firearms and could move with chilling speed."
Mr Jafferjee added: "This was a killing of a man who was in the process of removing his Christmas gift wrapping from the boot of the car and was thus entirely defenceless as he was shot."
He said the "terrifying incident" was witnessed by innocent members of the public who had been Christmas shopping.
Mr Brown's girlfriend told the court how she found his body lying by the car after he was shot.
She said: "I grabbed his face to see what was wrong with him and his eyes started rolling and blood started running out. That's when I realised something happened."
In a victim impact statement she said the killing was a "mindless, malicious and selfish act" that had been like a "horrible nightmare".