Armed police stormed a family's home after their teenage son was spotted playing with a toy gun in his bedroom.
The family denounced the police's "heavy-handed tactics"
An eye-witness had seen Olly Trimbos, 15, playing with a plastic BB gun and raised the alarm fearing it was real.
Officers burst through the door after the family had just finished dinner and handcuffed Olly and his father John.
Mr Trimbos said it was like a scene out of "a Bruce Willis movie" when police smashed in the door of his flat in Belsize Park, north London.
The father-of-two said the armed officers had flak jackets, helmets and goggles.
"They just said: 'Police, put your hands up and walk towards us slowly' so I did - I didn't have any choice," said Mr Trimbos, 42.
Father and son were taken outside for an hour while officers searched the property, finding only the plastic pellet-firing replica gun.
He described the experience as "utterly mortifying" and said it had left his wife, Olly, and his other seven-year-old son traumatised.
"Poor Felix - afterwards I picked him up and his whole body was trembling, he burst into tears," he said.
He criticised the police for "heavy-handed tactics" and said he intended to make an official complaint.
The information about the boy had come from a "credible witness", experienced in dealing with firearms, a police statement said.
Scotland Yard said the gun was a replica Heckler and Koch MP5 and that it was "not a toy".
"It is properly described as a replica rifle and not a toy," said a police spokesman.
The spokesman said police had apologised and that no complaint had been received.
She said arrangements had been made for the family's front door to be repaired.