Police arrested a 12-year-old boy at gunpoint after they raided his home believing a toy pistol he was playing with was real.
Up to 25 officers with sniffer dogs stormed Kai Agyepong's family home in Somers Town, Camden, before leading him away in handcuffs after a passer-by claimed she had seen a black male with a gun.
But the schoolboy had been playing with a BB pellet gun in the living room.
Kai was playing on a laptop on the sofa with his mum Alice, who was sleeping, when the armed officers raided the address.
Alice woke up to find her terrified boy had a red laser guided gun aimed at him as he was arrested and put in a police car outside.
But once police realised he was playing with a toy he was de-arrested and they apologised to him.
Alice criticised the police for their actions, saying her family felt "utterly violated".
The mum-of-three, who also has two daughters living at home aged 16 and 23, told the PA news agency: "In my mind there was no question they were going to shoot us.
"Their guns were drawn in such a way they were aiming their rifles at me and my kids."
She said the Met had thrown "every single resource except a helicopter" at the incident, adding that in addition to the armed officers and dog unit, there were two vans of ordinary PCs and an ambulance.
She said after being shown the BB gun, the police still conducted a full search of the premises lasting more than an hour and her son had "undoubtedly" been racially profiled.
Following the incident Alice said Kai has been left traumatised and is now becoming anxious if she even leaves him just to nip to the shops.
"It was very, very humiliating but more than that, for me and my kids it was terrifying," she said.
Alice said the Met had explained the incident by saying senior gang members often leave knives and firearms with younger boys in the hope they will be less likely to be discovered.
Commander Kyle Gordon, the Met's lead for firearms, said: "There have been a number of well-publicised shootings in London in recent months where members of the public have been injured.
"As the public would rightly expect, we take every report of a firearm seriously in order to protect our communities.
"Officers attending reports such as this must treat them as genuine until they can verify whether or not an actual firearm is present.
"Based on the information at hand, the officers acted in line with their training and my expectations, enabling the incident to be concluded as quickly and safely as possible."
Commander Gordon said he had watched the body-worn video of the incident and said he was "content" with the officers' professionalism and how they had explained to residents what was going on.
"The reporting member of the public was right to call us and we would encourage others who see similar weapons to do the same," he said.
"We are committed to bearing down on violence and we rely on our communities to help us do this."
He added that Kai had been immediately de-arrested as soon as officers had established the only weapon in the house was the BB gun.
