Suicide bomber Salman Abedi is believed to have travelled to Syria and become radicalised before returning to the UK to cause carnage at a gig in the city where he was born.
The 22-year-old was the son of Libyan parents, who fled their native country and sought refuge in the UK.
But just five days before he massacred 22 people, including young children, he sounded normal, according to his father Ramadan, who denied his son was linked to the bombing.
Rejecting reports the bomber had recently returned to Britain from Libya, Mr Abedi said his son had visited Libya more than a month ago.
Speaking from Tripoli, Mr Abedi told the Associated Press: "We don't believe in killing innocents. This is not us."
Mr Abedi confirmed his son Ismail, who was born in Westminster in 1993, was arrested on Tuesday.
Further arrests were made on Wednesday.
According to France's interior minister, Salman Abedi has "proven" links with Islamic State (IS).
Gerard Collomb told French television that both British and French intelligence services had information that Abedi had been in Syria.
Mr Collomb said: "All of a sudden he travelled to Libya and then most likely to Syria, became radicalised and decided to commit this attack."
Born and raised in Manchester, Abedi grew up in a Muslim household but became a university dropout.
He was registered as living at Elsmore Road as recently as last year, where police raided a downstairs red-bricked semi-detached property on Tuesday.
He previously lived with his mother Samia Tabbal, father Ramadan and brother Ismail.
He is also thought to have a younger brother, Hashim Abedi, and a sister Jomana, whose Facebook profile suggests she is from Tripoli and lives in Manchester.
Salman Abedi had been a "regular kid", who went out and drank until around a year ago when he "dropped off the radar", the Times reported the bomber's former landlord's nephew as saying.
The paper quoted a friend as saying he had returned from a three-week trip to Libya in recent days.
Neighbours recalled an abrasive, tall, skinny young man who was little known in the neighbourhood, and often seen in traditional Islamic clothing.
He is thought to have lived at a number of addresses in the area, including one in Wilbraham Road, where plain clothes police made an arrest on Tuesday.
A family friend, who asked not to be named, said they were known to the Libyan community in the city and described Abedi as "normal".
He told the Press Association: "He was always friendly, nothing to suggest (he was violent). He was normal, to be honest."
Abedi is believed to have attended the Manchester Islamic Centre, also known as Didsbury Mosque.
Sheikh Mohammad Saeed said he believed Abedi had displayed a "face of hate" after the imam gave a sermon denouncing terrorism.
Fawaz Haffar, a businessman and trustee of the mosque, told reporters he did not know the bomber or recall seeing him at the mosque, but said he did recall Mr Abedi attending.
He added: "As far as I knew, he went back to Libya when things were much better over there, to work over there."
Burnage Academy for Boys confirmed Abedi had been a pupil between 2009 and 2011.
He studied business and management at Salford University but dropped out of the course and did not complete his degree.
Abedi is not the first radical associated with the North West.
It has been reported he knew fellow Mancunian Raphael Hostey, who was once described as an "inspirational figure" for would-be jihadis.
Hostey, who left the UK in 2013, was believed to have been killed in a drone strike in 2016.
Libyan refugee Abdalraouf Abdallah was sentenced to five-and-a-half years in jail last year after helping Muslim convert and former RAF Iraq War veteran Stephen Gray try to get to Syria.
Abdallah, wheelchair-bound after he was shot in Libya in 2011, lived in Westerling Way, Moss Side, a short drive from Abedi's Elsmore Road address.
Gray, who lived at nearby Whitnall Street in the city, was jailed for five years for terror offences after he twice attempted to join jihadis in Syria.
Jamal al-Harith, who lived in Manchester and was known as Ronald Fiddler before converting to Islam, left the UK for Syria in 2014.
Earlier this year it was reported that he died after driving a truck packed with explosives into a military base in Mosul, Iraq.
It emerged he had received a compensation payment following his detention in Guantanamo Bay in the early 2000s.