Police fired an “unprecedented” 50 bullets to kill the three London Bridge terrorists because they believed the attackers were wearing suicide belts, the country’s head of counter-terrorism said.
Assistant Commissioner Mark Rowley said a member of the public also received a gunshot wound in the hail of bullets from the eight officers.
Seven people were killed and 48 injured in the attack on Saturday, with 21 fighting for their lives in hospital.
Twelve people have been arrested in connection with the atrocity after an armed raid in Barking, east London.
Mr Rowley said: “Eight police firearms officers discharged their weapons.
“Whilst this will be subject to an investigation by the IPCC, our initial assessment is in the region of 50 rounds - in the region of 50 bullets - were fired by those eight officers.
“The three attackers were shot dead.
“The situation these officers were confronted with was critical - a matter of life and death - three armed men wearing what appeared to be suicide belts.”
Mr Rowley added: “As the officers confronted a terrorist, a member of the public also suffered a gunshot wound.
“Although the injuries are not critical in nature, they are in hospital receiving medical attention.”
Mr Rowley said 36 people were being treated in hospital for various injuries, a number of them “extremely serious”.
Giving an update on the investigation outside New Scotland Yard, he said “significant progress” had been made in identifying the attackers.
It comes after police raids in east London, including activity at an address in East Ham on Sunday afternoon.
Mr Rowley revealed that the white Renault van used to target pedestrians on London Bridge had been “recently hired” by one of the terrorists.
He said that as well as more armed police across the capital “the public will also see an increased physical measures in order to keep public safe on London’s bridges”.
READ MORE: London terror attacks: What we know so far