Muslim leaders have called for a review of police policy on apprehending suspects after the shooting of a man unconnected to the London bombings.
Witnesses say the man was shot five times after being caught
They acknowledge the attacks have put police under pressure, but raise fears more innocent people may be killed.
Azzam Tamimi, of the Muslim Association of Britain, said he could not imagine how a restrained man could be a threat.
But Lord Stevens, the former Met Commissioner, warned against ending the "shoot-to-kill" policy for bombers.
Lord Stevens said he had adopted the policy before he had handed over to the present commissioner Sir Ian Blair "after much soul-searching over a great deal of time".
Writing in the News of the World, he called on the public to put themselves in the place of a firearms officer.
"Of course, in reality, it is a 'shoot-to-kill-to-protect' policy, to save innocent lives," he writes.
"The revelation that the man killed on Thursday by an armed police officer was, in fact, innocent of any bombing intent, may lead some to seriously question that policy.
"But we are living in unique times of unique evil, at war with an enemy of unspeakable brutality, and I have no doubt that now, more than ever, the principle is right despite the chance, tragically, of error."
Eyewitnesses described seeing the suspect chased by officers into Stockwell Tube station, held on the floor and shot five times in the head.
Mr Tamimi said: "I just cannot imagine how someone pinned to the ground can be a source of danger."
He added: "It doesn't matter whether he is a Muslim or not, he is a human being.
"It is human lives that are being targeted - whether by terrorists or, as in this case, by the people who are supposed to be catching the terrorists."
Public inquiry demand
Sir Iqbal Sacranie, of the Muslim Council of Britain, admitted that the bombings had put officers under pressure.
But he said: "It's vital that the utmost care is taken to ensure that innocent people are not killed."
Massoud Shadjareh, chairman of the Islamic Human Rights Commission, went further by calling for a full public inquiry.
He accused the police of using Israeli-style tactics against terror suspects.
"How can you shoot someone on mere suspicion?" he said. "You can't even put someone in prison on suspicion, how can you kill them like that?"
London Mayor Ken Livingstone said the police had acted in a way that they believed protected the lives of the public.
"This tragedy has added another victim to the toll of deaths for which the terrorists bear responsibility," he said.
John O'Connor, a former Scotland Yard commander, said it was likely that the investigation could lead to one or more officers being prosecuted.
He said concern would rise in the Met because of the case of Harry Stanley, who was shot dead by police six years ago while carrying a chair leg.
Two officers were arrested in June on suspicion of his murder, leading to criticism by police unions.
Glen Smyth, chairman of the Metropolitan Police Federation, described the man's death on Friday as "deeply regrettable".
"Police officers in these circumstances are expected to make split-second decisions that have life-long consequences," he said.
Shami Chakrabarti, the director of the human rights group Liberty, said her heart went out to the dead man's family and the officers involved.
"No one should rush to judgement," she said. "There must be a prompt, comprehensive and independent investigation into what happened.
"These are knife-edge split-second decisions made in moments of grave danger. We have a massive shared interest in the protection of innocent lives."
A Home Office spokesman refused to comment on the shooting, saying it was an operational matter for the police.