Archie Battersbee's life support has been withdrawn (6 August).
His mother said outside Royal London Hospital that he died at 12.15pm.
For the last few weeks, Archie's family have been fighting to keep him alive, taking the case to the European Court of Human Rights and making a last-minute plea to have the 12-year-old moved to a hospice.
However, after exhausting all possible legal routes, Hollie Dance, Archie's mum, is feeling 'pretty broken'.
Hollie, believes he blacked out after taking part in an online challenge.
Speaking about every parent's worst nightmare, Hollie said: "The last however many weeks since 7 April, I don’t think there’s been a day that hasn’t been awful really.
"It’s been really hard. Despite the hard strong face and appearance obviously in front of the cameras up until now, I’ve been pretty broken."
It's been a long battle for the young boy's family, with the Royal London hospital in Whitechapel, east London, had intended to end Archie's treatment at 2pm on 1 August, following previous judgements from the High Court and Court of Appeal.
However, the deadline was extended as the family continued to appeal - with a campaign spokesman confirming on Tuesday 4 August that they had made an application to the High Court to move Archie to a hospice to die, however, that application was unsuccessful.
Prior to this, on 15 July, the High Court ruled that Archie was 'brain stem' dead and that it was not in his best interests to keep him on life support.
Mr Justice Hayden described Archie's situation as a 'tragedy of immeasurable dimensions' after he was found unconscious at home.
But he said that there was evidence of 'significant injury' to 'multiple areas' of Archie's brain that painted a 'bleak' prognosis for the possibility of a recovery.
"Archie's mother described him as a fighter and I have no doubt he was," the judge said. "But the fight, if it can properly be characterised as such, is no longer in Archie's control.
"The damage to his brain has deprived him of any bodily autonomy.
"Eventually Archie's organs will fail and ultimately his heart will stop."
Archie's mother had asked for him to be given six months to recover, having argued that the decision to switch off his life support should be given to his family - and not the court.
"I don't think six months was not too much to ask for, before being dragged through a court," she said.
"I don't think I'm holding on to hope, I'm just asking for a realistic time for my child to recover from a brain injury.
"They wanted to turn the machine off on day three. What is the rush?
"I just think while Archie's progressing, I think it's important that evidence is actually put before a court. That he's progressing, not deteriorating like the doctor said that he would."
Hollie previously shared evidence that she claimed was proof her son was trying to breathe on his own and also claimed that her son had squeezed her hand as she sat by his bedside at the Royal London Hospital.
However, medical staff asserted that they saw 'no signs of life' in the schoolboy.
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