Khuram Shazad Butt, named Monday as one of the three London terrorists, was known to Britain’s MI5 intelligence service and even featured in a documentary entitled “The Jihadis Next Door” which aired last year, reports Times of Israel.

Neighbors identified Butt from the film’s footage Monday, pointing to a scene in which he is shown participating in a provocative prayer session at Regents Park, near London’s biggest mosque helping to display a black flag covered in white Arabic lettering similar to the one used by the Islamic State group, which took responsibility for the attack.

Butt is also seen in the film sprawling on the lawn and nodding as he listens to a sermon in which the speaker tells those gathered: “This is not the real life, my dear brothers. This is a passing time for us.”

Butt had worked for the London Underground for six months last year as a trainee customer services assistant, Transport for London told the BBC. British media said he had also worked at the fast food chain KFC and was a keen football fan.

British police identified the a 27-year-old Pakistan-born Briton as one of the three assailants, saying he was known to authorities, though they had no evidence he was planning an attack. They identified a second attacker who had not aroused suspicion prior to Saturday’s rampage that killed seven people.

As details about Butt emerged, however, they prompted questions of whether he could have been stopped sooner.

His extremist views had reportedly prompted numerous people to go to the authorities. They include a teenager who went to the same gym as Butt who said he was approached to join the Islamic State group, and a woman who told police she feared he was trying to radicalise children, The Times said.

Mohammed Shafiq, head of the Ramadhan Foundation think tank, said he was verbally abused by Butt in 2013 outside the British parliament.

He said Butt had called him a traitor in Arabic and accused him of being a government stooge.

Shafiq said Butt was at the time with radical preacher Anjem Choudary, the former head of a now-banned group called al-Muhajiroun.

Choudary was jailed for five-and-a-half years in September for encouraging support for IS jihadists.

Among those radicalised by Muhajiroun were the suicide bombers who killed 52 people on London’s public transport system in July 2005, and the men who murdered soldier Lee Rigby in the capital in 2013.

“I am not surprised that Khuram Butt carried out the terrorist attack and there are serious questions for the authorities,” Shafiq said.

One neighbor, Erica Gasparri, contacted police about 18 months ago. The 42-year-old mother of three was working at a local school when she noticed Butt, who was also known as Abu Mohamed, meeting with local children and trying to draw them into his radicalism.

“It was wrong what he was doing,” Gasparri said. “He kept talking about the Islamic State. I got very angry.”

Salaudeen Jailabdeen, who lived near Butt, said the alleged assailant had once been ejected from a local mosque for interrupting an imam. Another neighbor, Michael Mimbo, said he saw the van used in the attack near his home on Saturday, but didn’t see who was behind the wheel. He said the vehicle was seen going the wrong way down a one-way street and was later seen speeding off, followed closely by a small red car.

“We saw him many, many times around here,” said Salaudeen, a 40-year-old driving instructor.

“He used to be friendly but suddenly… he wasn’t acting as normal. He wasn’t aggressive; he used to chat but lately he was just ‘hi’ and ‘bye’,” he told AFP.

Salahudeen said the man had two children — a baby girl and a boy who used to be taken to the park by his father to play football.

The second alleged attacker was identified by police as Rachid Redouane, who alternately used the surname Elkhdar, and claimed to be Moroccan and Libyan. He used two different birthdates that would make him either 25 or 30, authorities said.

Police have not yet released the identity of the third person involved in carrying out the attack on London Bridge, where the van swerved into pedestrians, and in nearby Borough Market, where the knife-wielding assailants slashed and stabbed anyone in their path. Besides the dead, dozens more were wounded by the men, who wore fake suicide vests to make themselves look even more imposing.

All three were ultimately shot and killed by police. Twelve others taken into custody have since been released.