A minute's silence was observed in Britain at 11 a.m. local time (1000 GMT) in memory of those killed during the attack. London police have said all 12 people held since the attack late Saturday from the Barking neighborhood, have been freed. In a letter posted outside Tuesday, the Ummah Fitness Centre said staff would "help the police in any way we can" as investigators try to learn more about Khuram Shazad Butt, who was one of those who rammed a van into pedestrians on London Bridge and then slashed and stabbed people in nearby Borough Market. All three men were shot dead by police within eight minutes of receiving a 999 call. One of the attackers, Butt, had appeared in a documentary "The Jihadis Next Door" and was known to investigators but police said he was not believed to be plotting an attack. Another of the attackers has been named by police as Rachid Radouane, 30, from Barking. The married father-of-two, who worked for London Underground as a trainee customer services assistant for nearly six months last year, could be seen in the programme arguing with police officers in the street, after displaying a flag used by so-called Islamic State in a London park.  A child looks at the floral tributes after a vigil for victims of Saturday's attack in London Bridge, at Potter's Field Park in London, Monday, June 5, 2017. London Mayor Sadiq Khan said questions would need to be asked about what the police knew about Butt.
– One of the three suspects in the London Bridge attack was known to police. Khuram Shazad Butt, who may have had links to jihadist group Al-Muhajiroun, had been the subject of a Metropolitan Police investigation beginning in 2015. However, the investigation was "prioritized in the lower echelons" because "there was no intelligence to suggest that this attack was being planned," a rep tells the BBC. A man and a woman living in east London had both contacted police about Butt, with the woman suggesting he had tried to radicalize her children. According to the Times, Butt had links to both radical Islamic preacher Anjem Choudary and Mohammad Sidique Khan, who planned the 2005 London bombings. Khan worked at an Ilford fitness center that Butt, a 27-year-old father of two, would frequent to try and radicalize youth, the Times reports. Butt also appeared in a 2016 Channel 4 documentary about Islamist extremists with ties to Choudary. He was seen arguing with police after carrying an Islamic State flag. Yet Butt still managed to get a job with the London Underground. The UK citizen born in Pakistan served as a trainee customer service assistant for almost six months in 2016, per the BBC. "People are going to look at the front pages today and they are going to say 'how on earth could we have let this guy—or possible more—through the net,'" Foreign Secretary Boris Johnson says, per Buzzfeed. Police previously identified Rachid Redouane, 30, who claimed to be Moroccan and Libyan, as another of the attackers. On Tuesday, they named the third: Youssef Zaghba, 22, believed to an Italian national of Moroccan descent, reports the AP. Neither he nor Redouane appeared to be on police radar prior to the attack.