Abedi's father returned to the African nation in 2011 after the rebels overthrew the government and his wife joined him earlier this year.
After getting word that Salman Abedi and his brother Hashim were getting into trouble in England, Ramadan Abedi sent for his boys and they joined their parents about a month ago, a family friend in Libya told CNN.
But Salman Abedi came back to England last week after telling his father he wanted to make a pilgrimage to Saudi Arabia, the source -- who asked not to be named for discussing sensitive family matters -- and a source in the Libyan community of Manchester, told CNN.
Three days after he returned, Salman Abedi went to an Ariana Grande concert where authorities said he detonated a bomb that killed 22 fans -- many of them children and young people
-- who were leaving the Manchester Arena. Scores more people were hurt, some critically.
Abedi, 22, is believed to have died in the powerful blast, but a coroner has yet to officially identify his remains, Manchester police said.
On the radar
Abedi was already known to authorities, UK Home Secretary Amber Rudd said Wednesday. But it's not yet clear why he was on their radar.
Rudd said authorities were aware of him, to a point. "The intelligence services know a lot of people, and I'm sure we will find out more what level they knew about him in due course," she told the BBC.
"But at the moment all they have confirmed is that they did know about him, and as I say we will find out more when the operation is complete."
Authorities now are working to track down Salman Abedi's associates.
"It is very clear that this is a network we are investigating," Greater Manchester Police Chief Constable Ian Hopkins said Wednesday.
Rudd had earlier told the BBC that the bomber may not have worked alone.
The motive for carrying out the attack remained unknown on Wednesday morning. ISIS claimed responsibility, saying Abedi was a "soldier of the caliphate," but offered no evidence.
French Interior Minister Gérard Collomb told BFM-TV that Abedi had "proven links to ISIS," though he did not elaborate. Rudd declined to comment on the claim.
Time in Libya
The Abedi family friend told CNN the two brothers wanted revenge for a friend who was killed by a gang.
Their father, a police officer in Libya, got them to go there and took away their passports.
Salman Abedi got his travel documents back by saying he wanted to make an Umrah, or pilgrimage, to Mecca, the friend told CNN.
US military officials assigned to Africa Command told CNN that Salman Abedi had been in Libya for three weeks
That specific information has been shared between US and British intelligence services, the US officials said, adding they currently have "high confidence" the information is accurate.
The trip raises questions about what he was doing there, whom he met with and whether he received training or support.
Abedi was a student at the University of Salford -- Manchester's third largest university -- where he studied business and management in the 2015-2016 academic year. He was enrolled for a second year, but hadn't been attending classes, nor had he been active in school life, according to those who knew him.
Abedi did not stay on campus in Salford, instead living in the Fallowfield area of south Manchester.
Suspected bomber was lonely child
Details are slowly emerging about Abedi, who was born and raised in the United Kingdom, according to Prime Minister Theresa May.
Abedi had seemed like a lonely child, who kept himself to himself, according to long-time family friend Akram Ben Ramadan, a British Libyan who had known Abedi and his brother, Ismael, since the Abedis were children. There were four children in the family in total -- three boys and one girl.
Abedi went to a Manchester school, Burnage Academy for Boys, from 2009 to 2011. The school declined to comment on his time there but sent a message of support to all those affected by the attack.
Ramadan, who had not seen Abedi much in recent years, said he had noticed that he had begun to dress "Islamically," in a long robe, and was growing a beard.
The Manchester Islamic Centre and Didsbury Mosque, a couple of miles from Abedi's home, condemned the "horrific" bombing in a statement on its website Wednesday.
And Fawzi Haffar, a trustee of the center, told reporters gathered outside the large, red brick mosque -- which welcomes thousands of Muslims every week -- that a small number of media reports that claimed the bomber had worked at the site were "not true."
Monday's attack "shocked us all," he said. "This act of cowardice has no place in our religion or any other religion for that matter. We encourage anyone, and I repeat anyone, who may have information about the individual involved to contact the police without any delay."