But Butt, 27, was not the typical resident of the East London neighborhood of Barking.
As police announced the arrest, they also released the name of the third attacked in involved in Sunday's attack.
"Shortly after that, we saw ambulances and police cars rushing to the scene with the sound of sirens filling the air that night while helicopters were hovering overhead for two to three hours", recalled the PhD candidate in Chemistry at Imperial College London.
The two main candidates for prime minister - the incumbent, May, and the challenger, Jeremy Corbyn - traded barbs Monday over how security services can better protect the public after three mass-casualty attacks in as many months.
Redouane was not known to those authorities.
Butt was one of 3000 subjects of interest in terrorism investigations - but police said he was not perceived as a priority as they had no intelligence to suggest that he and his co-conspirators were planning a terror attack. An armed unit killed the trio with 50 shots within eight minutes of the alarm being raised.
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.
"The narrowing of the gap seems to be driven by supporters of other parties coalescing around Corbyn, and by very high support among young people", says Follett.
The family of Mr McMullan, who lived in Hackney, east London, have been told by police his bank card was found on one of those killed during the atrocity.
Campaigning was suspended on Monday, in the wake of the weekend's terror attack on London Bridge.
After that, Amato said, any time Zaghba was in Italy, he was always tracked by Italian intelligence officers. There are 500 current investigations involving 3,000 potential suspects.
At the time of the attack he was working in a London restaurant and continued to have contacts with his mother in Italy, which he visited previous year, Corriere wrote.
May said the attacks were inspired by what she called a "single, evil ideology of Islamist extremism" that represented a perversion of Islam and of the truth. "You will not win", he said.
It provided a kaleidoscope of London's diversity, with Buddist monks in saffron robes, Christian clerics in purple cassocks and Muslims in black T-shirts bearing the words "I am a Muslim: Ask me anything".