Last Updated Jun 6, 2017 6:46 PM EDT
LONDON -- Details emerged Tuesday about: a Pakistan-born failed customer service clerk with links to one of Europe's most prolific hate preachers, a Moroccan pastry chef whose partner said he once went swimming rather than see his daughter and an Italian man who told authorities he "wanted to be a terrorist."
At least two of the men were known to British intelligence and law enforcement officials, raising questions about whether anything could have been done to stop the attack. All three had connections to the same East London neighborhood, CBS News' Anna Werner reports. But it's unclear how they eventually teamed up to drive a rented van into pedestrians on London Bridge and then attack others with knives.
and nearly 50 wounded. All three of the attackers were shot dead by police.
British Foreign Secretary Boris Johnson said it was fair to ask how the attackers "slipped through our net."
Security has become a key issue in the run-up to. British security officials said none of the men was considered violent, but they acknowledged the difficulty of predicting whether extremists will turn dangerous. The assault was the third attack in three months in which most of the assailants had been on authorities' radar at some point.
As the investigation expanded to look at how the men knew one another and whether they were part of a larger conspiracy, Pakistani intelligence authorities swooped Tuesday into the town of Jhelum, where Khurum Butt lived until the time he was 7, when he moved to Britain. His cousin, 18-year-old Bilal Dar, told The Associated Press that Butt's uncle was taken in for questioning. It was unclear if he was detained.
"Our family is hurt by what he did," Dar said in the town about two hours east of Pakistan's capital. "This has destroyed our family's pride."
Butt, 27, embraced radical Islam during his time in London and was once filmed in a documentary called "The Jihadis Next Door." In the film, he was seen with a group unfurling a black-and-white flag associated with the Islamic State group. The men were followers of Anjem Choudary, a preacher who was jailed for his support of the Islamic State and who once praised the Sept. 11 attackers.
It is thought that Choudary played a key role in Butt's radicalization, according to a British government official who spoke on condition of anonymity because he was not authorized to talk about the ongoing investigation. Choudary's now-banned al-Muhajiroun group was linked to one of Butt's alleged connections, Sajeel Shahid, according to the British government official who again spoke on condition of anonymity.
Shadid allegedly provided al Qaeda terror training to Mohammed Siddique Khan, one of the four suicide bombers who killed 52 people during London's morning rush hour in 2005. He was also accused of training other terror suspects in Britain.
During his time in Britain, Butt once worked for Transport of London as a customer service clerk but failed his probation after a few months on the job. He also worked at Kentucky Fried Chicken and used a gym in east London. In his spare time, he tried to recruit followers to the Islamic State group -- a practice that prompted a neighbor to report him to the police in 2015.
He was one of about 3,000 suspects who were known to British authorities but not part of 500 active investigations.
"The problem occurs when we know someone is moving in extremist circles but we don't have evidence to indicate that they are plotting an attack," said the British government official who spoke on condition of anonymity. "That's where the question of resources comes into play."
Police identified the second attacker as 30-year-old Rachid Redouane, also known as Rachid Elkhdar, who claimed to have both Moroccan and Libyan roots and worked as a pastry chef in Ireland, where he had lived in the past five years as well the east London suburb of Dagenham.
He married a British woman named Charisse O'Leary, who posted on Facebook last month that Redouane was negligent in seeing their young daughter and on one planned visit, she said he told her: "I'm going swimming." The couple is thought to have split. O'Leary was one of 13 people arrested after Saturday's attacks. Twelve were later released. One man is still being held.
Redouane was never under surveillance by Irish authorities, and Justice Minister Frances Fitzgerald urged caution in speculating about his movements.
The third attacker was identified as Youssef Zaghba, a 22-year-old Italian national who was reportedly working in a London restaurant. Italian police confirmed to CBS News that Zaghba's father is Moroccan, his mother is Italian, and that Zaghba did not live in Italy.
Zagbha was stopped in March 2016 while trying to board a direct flight to Istanbul. Police told CBS News that they found ISIS material on his cell phone, after which he was placed on a watch list. An Italian prosecutor says Zaghba told authorities after being stopped last year at Bologna's airport that he "wanted to be a terrorist," but then quickly corrected himself.
There was not enough evidence to arrest or charge Zaghba when authorities questioned him at the Marconi airport on March 15, 2016, Bologna prosecutor Giuseppe Amato said Tuesday. Amato told Italy's Radio 24 that Zaghba was flagged to British authorities as a "possible suspect."
After that, Amato said, any time Zaghba was in Italy, he was always tracked by Italian intelligence officers.
"We did everything we could have done," he said. "But there weren't elements of proof that he was a terrorist. He was someone who was suspicious because of his way of behaving."
Italy has expelled nearly 50 people in the past two years who were suspected of extremist activities but for whom there was insufficient evidence to bring formal charges. Zaghba's Italian citizenship prevented such an expulsion, Italian daily Repubblica reported.
His mother said her son used to show her videos of Syria and wanted to go "because it was a place where you could live according to a pure Islam."
Valeria Collina was quoted by Italian weekly news magazine L'Espresso as saying she last spoke to her son Thursday and now realizes it was a goodbye call. She said she tried to keep him away from radical friends, but "he had the internet and from there he got everything."
Prime Minister Theresa May, who called the snap election in hopes of strengthening her mandate for discussions over Britain's exit from the European Union, has come under fire for the cuts to police numbers in recent years. A string of opinion polls over the past couple of weeks have pointed to a narrowing in the gap between her Conservative Party and the main opposition Labour Party.
The number of police officers in England and Wales fell by almost 20,000 between 2010 and 2016 -- years when May, as home secretary, was in charge of policing.
The country's official terror threat level remains at "severe," one notch below the highest.