Three teenage boys were being questioned today after a 15-year-old boy was stabbed to death in a planned attack by suspected rival gang members as he arrived at school.
Zac Olumegbon, from Brixton Hill, south London, and a friend were ambushed by four young men at the gates of Park Campus School in nearby West Norwood.
A post-mortem examination at Greenwich Mortuary found the cause of death was stab wounds to the chest.
A local shopkeeper described how Zac fell into the arms of a teacher after Friday's attack.
Saima Sadfdar, who runs a corner shop, said: "She had her hands open but it was too late and he collapsed in her arms."
Police believe four black males arrived in a car before the attack and a confrontation took place outside the school involving the two victims.
The pair were then chased into Gipsy Road Gardens, where Zac was repeatedly stabbed.
His 14-year-old companion ran back to the school to seek safety but was attacked in the grounds and stabbed in the arm.
Police, London Ambulance Service and an air ambulance attended the scene at 8.50am, where they found Zac suffering multiple stab wounds.
He was taken to a south London hospital and confirmed dead shortly after arrival.
His companion was also taken to a south London hospital, suffering minor injuries.
Witnesses said the attackers were waiting in the car, which was parked close to the school for youngsters excluded from mainstream education.
Ms Sadfdar said: "I was told there were three or four people with a big knife.
"Apparently one of the teachers realised something was going on and ran out to help."
She said she knew Zac, who was "no trouble".
Police confirmed one line of inquiry was that the murder was motivated by gang rivalries.
The Metropolitan Police Homicide and Serious Crime Command launched a murder inquiry under Det Ch Insp John McFarlane.
Mr McFarlane said: "I am now satisfied this was a planned attack, with four black males arriving in the area in a car.
"A confrontation took place outside the school involving the two victims and the suspects. The victims were chased into Gipsy Road Gardens where, sadly, the 15-year-old suffered fatal injuries.
"The 14-year-old then ran back to the school to seek safety, but was attacked in the grounds of the school, suffering minor injuries.
"Following the attack the four males left in the car and headed in the direction of Gipsy Hill.
"I am appealing to anyone who was in the area and witnessed anything to contact police on 020 8721 4205 or, to remain anonymous, call Crimestoppers on 0800 555 111."
The road was cordoned off by police on Friday as blue-suited forensics officers examined a stretch of pavement.
Pupils at the school, which has 80 places, were kept inside for questioning by teachers and police.
Zac's family was too upset to comment but four of his friends laid flowers near the scene.
One of them, Cumi Simpson, said the boy, who she knew as "little Zac", would be missed.
"He was just a bubbly character. I miss him so much already. I just want to lay these flowers for him," she said.
"I've spoken to his family and obviously they are very upset."
A tribute laid with the flowers read: "I will always remember you, the good, the bad times, no matter what.
"I will always miss you and see you when I get up there. RIP. No matter what I miss you, I love you, little Zac."
Tributes were also paid to him on microblogging site Twitter and social networking site Facebook.
More than 3,000 people joined a Facebook group called R.I.P Lil Zac.
Jesse Gassongo-Alex, an aspiring actor, said he had known the victim since they were aged six.
He said they both went to the Brit School in Croydon but the dead teenager was "kicked out".
Writing on Twitter, Mr Gassongo-Alex said: "Love you my boy, l'il Zac. Still can't believe you gone Zac."
Another former school friend added: "Just heard the news about Zac getting stabbed to death in West Norwood. Just tragic, another young life wasted."
On Facebook, one friend claimed the victim was stabbed up to 15 times. Oscar Floris said: "It's too much."
Zac was the 13th teenager to be killed in the capital this year as senior officers pull out all the stops to keep a lid on violence among young people.
Hailed as the first of its kind on its launch two years ago, Park Campus is a specialist school educating some of London's most troubled young people.
Rose Gabriel, who lives in the street, said it had a bad reputation.
She said: "I can't say it is that much of a surprise. We were kind of expecting something to kick off at some point.
"It's a shame it had to happen like this."
Park Campus head teacher Richard Leonard said: "This is a terrible tragedy and the whole school is in shock.
"We will be providing all the support we can to pupils and their families as the school community tries to come to terms with this awful loss."
Three other teenagers arrested on Friday were released on bail.Reuse content