The attacker reportedly strapped a fake bomb to his body and stabbed a man and a woman to death at Fishmongers' Hall during a conference about rehabilitating offenders on Friday.
The attacker has now been identified as Usman Khan (28), a convicted terrorist.
Here are more details.
Khan apprehended by locals; shot dead by police
Metropolitan Police Assistant Commissioner Neil Basu said Khan was invited to the conference called 'Learning Together' and sat through the morning session.
The attack began inside the Fishmongers' Hall and continued onto the London Bridge.
Thereafter, Khan was tackled and restrained by locals and shot dead by armed officers.
Two people were killed and three others—one man and two women—were injured.
Who was the attacker?
Usman Khan was identified after he was shot dead at around 2 pm.
Khan, who spent his late teens in Pakistan, was convicted for terrorism offenses in 2012 after he pleaded guilty to plotting to bomb the London Stock Exchange in 2010.
Arrested in December 2010, he was released on parole in December 2018.
During the Friday attack, he was wearing an electronic tag.
2010 bombing plot
Khan among group that plotted to bomb London Stock Exchange
At age 19, Khan was among the youngest in a group who plotted to bomb the London Stock Exchange, Big Ben, and Westminster Abbey in 2010.
A handwritten list of names and addresses of potential targets was also obtained from the terrorists. The targets included Boris Johnson, then-Mayor of London.
However, their plot was disrupted in a concerted effort by the MI5 and police.
Khan once planned to set up terrorist camp in Kashmir
Reportedly, Khan had also once planned to set up a "terrorist military training facility" at a Madrassa on the land owned by his family in Kashmir. He had planned "to recruit young British Muslims to go there and train," as per sentencing remarks from his 2012 conviction.
Khan among 'more serious jihadists' in 2010 bombing plot
Including Khan, nine men pleaded guilty to the 2010 Stock Exchange plot.
The sentencing judge, Justice Wilkie, described Khan and two others as the "more serious jihadists" among the group, adding that they shouldn't be released until they are no longer a threat to the public.
Justice Wilkie said Khan should serve a minimum of eight years of his 16-year sentence.
Khan received discount on sentence for pleading guilty
However, Khan, believed to have been a supporter of extremist group al-Muhijaroun, received a 20% discount on his sentence for pleading guilty. He was subjected to a terrorism notification period of 30 years. The 2010 plot was also said to have been inspired by al-Qaeda.
PM called for 'appropriate sentences for terrorists'
Meanwhile, addressing the attack, British Prime Minister Boris Johnson said on Friday that reporters had "long argued" that it was a "mistake to allow serious and violent criminals to come out of prison early."
Johnson pushed for "appropriate sentences for dangerous criminals, especially terrorists."
He also praised the locals who apprehended Khan, describing them as "the very best of our country".