There is no evidence Mark Duggan opened fire at police before being shot dead by a firearms officer, the Independent Police Complaints Commission has said.
Mr Duggan, 29, whose death sparked the first riots in Tottenham, died from a single bullet wound, an inquest heard.
The police watchdog said ballistic tests showed "no evidence that the handgun found at the scene was fired".
BBC News understands firearms officers discharged their weapons in the belief there was a threat to human life.
Their guidelines allow them to open fire in such circumstances.
Establish the facts
Mr Duggan, a father of four, was shot in Ferry Lane, Tottenham, north London, on Thursday, as specialist firearms officers attempted to make an arrest.
A key witness, the driver of the minicab in which Mr Duggan was travelling, has yet to give his version of events. He is understood to be in a severe state of shock.
Investigations by the IPCC show two shots were fired by a Scotland Yard CO19 firearms officer.
The initial results confirmed a bullet found lodged in a police officer's radio was a "jacketed round" - a police issue bullet consistent with being fired from a force Heckler and Koch MP5.
Forensic officers have told the IPCC it may not be possible to "say for certain" whether the handgun found near Mr Duggan was fired.
Further tests on the weapon, which had been converted from a blank-firing pistol to one that shoots live rounds, are being carried out to establish this.
Search for truth
The IPCC said it was not a replica and was an illegal firearm.
Further tests are being carried out on a "bulleted cartridge" found in the magazine.
In response to the findings, the Met said it was in everyone's interests "the IPCC are able to establish all the facts of the events of last Thursday so that there is a complete understanding of what happened".
An inquest into Mr Duggan's death was opened at North London Coroner's Court in High Barnet and adjourned until 12 December.
Colin Sparrow, deputy senior investigator for the Independent Police Complaints Commission, which is looking into the shooting, told the hearing the inquiry could take up to six months.
A statement released by Mr Duggan's family said they were "deeply distressed" by the disorder affecting communities across England.
It read: "We want to establish the truth about Mark's death.
"The family want everyone to know that the disorder going on has nothing to do with finding out what happened to Mark."