The attacker - convicted terrorist Usman Khan, 28 - had been released from prison on licence a year ago.
Khan, who is believed to have been 15 at the time, was interviewed in response to a police raid on his home.United Kingdom authorities have confirmed Khan was a jihadist and considered a serious threat to the public.
In 2012 Khan, from Stoke in central England, was jailed along with eight others in a terrorist group inspired by Al-Qaeda that had plotted to bomb targets including the London Stock Exchange.
Khan, who was born in Britain, had plans for a "terrorist military training facility" disguised as a madrasah (Islamic religious school) on land owned by his family in Kashmir, according to sentencing remarks. Six people died, including the assailant and the policeman he stabbed, and at least 20 were injured in what police called a "marauding terrorist attack". He was released from prison in December 2018 on licence and clearly, a key line of enquiry now is to establish how he came to carry out this attack. A victim who had been in critical condition has improved and is now listed as stable, officials said.
It's thought he was a course co-ordinator for the Learning Together programme which was hosting a conference at Fishmongers' Hall attended by Usman Khan.
It was a snippet of conversation, along with other intelligence about a plot to bomb the London Stock Exchange, that prompted British police to arrest Khan - then 19 years old - and a group of older men on December 20, 2010.
Khan was tackled by members of the public - including former prisoners - before police shot him dead. They drag a bystander off of Khan, then shoot and kill Khan.
Police were called to the north side of London Bridge at 1.58pm on Friday, after reports of a stabbing near Bank station and Fishmongers' Hall.
Video footage showed a number of people, one with a fire extinguisher and another armed a narwhal tusk, taking Khan to the ground before the arrival of police.
Mayor Sadiq Khan praised the "breathtaking heroism of members of the public who literally ran towards danger not knowing what confronted him".
"We do have to look again at the sentencing system", he said.
In an interview on Sky News, Prime Minister Boris Johnson said that those individuals represent "the best of our country".
Jeremy Corbyn, leader of the main opposition Labour Party, criticised the government's sentencing policies."There's got to be a very full investigation", Mr Corbyn said. Usman Khan's 2012 arrest came after he was overheard by British security services discussing how to use an al-Qaida manual he had memorised to build a pipe bomb.
Armed police surround the knifeman on London Bridge.
Khan was shot and killed by police after flashing what appeared to be a suicide vest.
He was Cambridge and his father also said the entire community was in "shock" after the attack that left another woman dead and three more seriously injured. ISIS had claimed responsibility for the June attacks.
"For the Conservatives, there will be questions for the Home Secretary about why, only three weeks ago, she reduced the terror threat in the United Kingdom from severe to substantial", Fisher said, adding that cuts to police numbers could have had an impact on their surveillance of Khan.
Friday's attack has raised hard questions for the United Kingdom government and security services. The MI5 determined that they had planned a series of attacks akin to the multi-day terrorist assaults in Mumbai in 2008, but this time targeting the British Parliament.