Three teenagers and a man have been jailed for their part in the killing of a 15-year-old boy in Croydon.
Jermaine Goupall was fatally stabbed on 8 August in south London.
Adam Benzahi, 21, Samuel Oliver-Rowland, 18, and Junior Simpson, 17, were all convicted of murder and given life sentences.
Saskia Haye-Elliot, 18, was sentenced to 12-and-a-half years in jail for manslaughter after being found not guilty of murder.
A fifth defendant, Daniel Luke, 18, was acquitted of both murder and manslaughter following the five-week trial at the Old Bailey.
The circumstances of the fatal attack had been predicted in lyrics penned by Simpson, the court heard.
Judge Anthony Leonard QC told Simpson: "Music was a big part of your life but it's clear so was your absolutely chilling addiction to holding and using knives."
Mr Goupall's suffered a single stab wound to his femoral vein after being ambushed by a number of people wearing balaclavas outside a Costcutter on Green Lane, in Thornton Heath.
The 15-year-old was pronounced dead at the scene.
The suspects, all from Croydon, denied any involvement in the murder, but were identified through mobile phone analysis and CCTV images, according to the Met Police.
The killing came amid heightened tension between two gangs, fuelled by a series of "taunting" music videos posted online.
Judge Leonard said the killing was aggravated by the fact it involved "significant planning and premeditation", but said it was "pure chance" that Jermaine was targeted.
Police believe Mr Goupall was not himself an active gang member.
Det Ch Insp Tony Lynes described the murder as "senseless" and one which "appeared to stem from gang rivalry and violence".
He added: "I can only imagine the fear Jermaine felt as he was attacked.
"These four defendants denied involvement, but the weight of evidence against them was enough to convince a jury of their guilt.
"We now have a family left utterly devastated and the lives of all involved blighted forever."
Benzahi was jailed for life and ordered to serve a minimum of 22 years in prison; while Oliver-Rowland and Junior Simpson were given a minimum term of 20 years and 18 years, respectively, in jail.