The officers who shot Jean Charles de Menezes were convinced he was a suicide bomber who could only be stopped by an "instant killing", an inquest heard today.
Coroner Sir Michael Wright said the innocent Brazilian was shot at Stockwell Tube station even though no surveillance officer positively identified him as a terrorist.
He outlined how senior officers overseeing the operation at Scotland Yard thought he was on-the-run failed suicide bomber Hussain Osman.
The crucial 33 minutes as Mr de Menezes travelled to work on July 22 2005 were dramatically relived on the first day of the inquest into his death.
Sir Michael recreated detectives' desperate efforts to track down the men responsible for attempting to create carnage on the London transport network.
Jurors heard how two specialist marksmen rushed on board a Tube train and shot the 27-year-old in the head as he was pinned to his seat by an undercover officer known as Ivor.
The two firearms officers - identified only as Charlie Two and Charlie 12 - will give evidence in public for the first time later in the inquest.
Sir Michael said: "Both officers state that they were convinced Mr de Menezes was a suicide bomber, that he was about to detonate a bomb and unless he was prevented from so doing everybody present in that carriage was going to die.
"Each officer says he was convinced that an instant killing was the only option open to him.
"Each reached over Ivor and fired several times at point-blank range into Mr de Menezes's head."
Sir Michael told the jury: "It will be for you to consider what level of identification was made at different stages, what was communicated to the firearms officers, and what those officers believed the position to be."
The coroner said the electrician was killed instantly: "He can hardly have had any opportunity to appreciate what was happening."
A post-mortem examination revealed Mr de Menezes had been shot seven times in the head.
The first evidence to be heard during the 12-week inquest at the Oval cricket ground outlined apparent misunderstandings between surveillance and firearms officers.
Sir Michael said: "It does appear that by the time Mr de Menezes had actually entered the Underground system at Stockwell station, no member of the surveillance team had positively identified him as Osman.
"But at New Scotland Yard there does appear to have been a perception that Mr de Menezes had been positively identified as Osman."
The marksmen sent to the scene also believed Mr de Menezes was their suspect.
One of the firearms officers, identified as Ralph, recalled hearing over the surveillance radio the message, "It's definitely our man", and that he was "nervous and twitchy".
The coroner told jurors that despite a series of independent inquiries into the shooting and an Old Bailey prosecution the inquest is a "fresh approach".
He warned the six women and five men to ignore often "very inaccurate" media speculation and said the responsibility for determining the facts was "yours and yours alone".
Senior Met officers will have watched the first hours of the inquest extremely closely.
Commissioner Sir Ian Blair has already described it as the biggest test for his force since the Stephen Lawrence inquiry.
Although little new evidence is expected to emerge, the verdict will have wide-ranging repercussions.
Sir Michael said Mr de Menezes was an innocent man, legally in Britain, who did nothing to contribute to his death.
He said: "It must be stated at the outset of this inquest with the greatest possible emphasis that in truth Mr de Menezes was in no way associated with bombs, explosions or any form of terrorism."
Speaking at the end of the day, cousin Patricia da Silva Armani said she hoped a "long and painful few months" would bring her family nearer the truth.
She said: "Today is the first day and we hope it will bring our family closer to the truth. We are hoping that at the end we will get closer to knowing how my cousin died.
"Hearing it again brought back the pain and anguish since Jean's death.
"This will be a long and painful few months but we will be here until the end to get the truth."
The inquest was adjourned until tomorrow when jurors will be taken on a tour of sites including Stockwell Tube station, the Scotia Road flats where Mr de Menezes lived, and Scotland Yard.