Friends and passers-by rushed to help a teenage schoolboy who was stabbed to death outside a busy shopping centre in broad daylight, Scotland Yard said.
The Metropolitan Police were called to Broadway in Stratford shortly after 3pm on Thursday following reports of a stabbing.
The 15-year-old was attacked on or after getting off a bus which had stopped close to the Stratford Shopping Centre, the force said.
Friends rushed to help him and members of the public performed first aid at the scene, it added.
Police and paramedics found the schoolboy with “critical injuries” and despite battling to save his life he was pronounced dead at the scene near the shopping centre at 3.49pm.
The force said his next of kin have been informed but formal identification and a post-mortem examination were yet to take place.
Detective Chief Inspector Chris Soole, who is leading the investigation, branded it a “senseless attack” and said a murder investigation had been launched.
He added: “First and foremost are thoughts are with this young man’s family and friends.
“They so tragically are having to come to terms with this terrible loss of life.
“The victim of this stabbing was a schoolboy with his whole life ahead of him. He had everything to live for.
“This was a senseless attack and we share the concern and alarm this murder will no doubt cause in the local community.
“What we know now is that the victim was attacked on or shortly after alighting from a bus which stopped very close to Stratford Shopping Centre near Tramway Avenue.
“An altercation took place and he was fatally wounded.
“We know that the victim’s friends came to his aid and members of the public provided first aid at the scene.”
DCI Soole said the attack took place in a busy area and appealed for witnesses to come forward.
A second boy, aged 15, was also found with stab injuries was taken to an east London hospital, where his injuries are said to be not life-threatening.
The force said no arrests have been made and inquiries are ongoing.
A blue and white police forensic tent has been set up in front of an entrance to the Stratford Shopping Centre, which appeared to have been closed by police.
Forensic officers in blue boiler suits can be seen within the cordon.
A witness to the incident told the PA news agency that the attack happened outside a McDonald’s restaurant next to the entrance.
“At that moment there were not many people around him so I could see him all covered in blood. He was in pain and tried getting up,” they said.
“There were people around gathering. It was scary as you did not know if any of them could have had a knife too.”
One stall worker told PA he saw paramedics trying to perform first aid to a “young guy”.
“I saw police around here and one person was on the floor, I think they stabbed him,” he said.
“It was a young guy. He was a black guy on the floor. I think the ambulance guys tried to give him first aid.”
Uniformed officers continue to man the barriers while a number of squad cars remain in the area.
A section 60 order, giving officers the power to stop and search in the area, has been implemented.
Witnesses should call the police on 101 quoting reference CAD 4644/01OCT19 or Crimestoppers anonymously on 0800 555 111.