The Manchester bomber's sister has claimed he was driven to murder because he wanted revenge for "the explosives America drops on children in Syria".
Jomana Abedi, 18, described her older brother Salman as kind and loving and said she was surprised that he had detonated a suicide bomb, killing 22 people after an Ariana Grande concert at Manchester Arena on Monday.
Speaking to the Wall Street Journal she said she thought he was driven by what he saw as injustices.
"I think he saw children-Muslim children-dying everywhere, and wanted revenge", Miss Abedi told the paper.
"He saw the explosives America drops on children in Syria, and he wanted revenge. Whether he got that is between him and God," she added.
A family friend also alleged that it was the murder of Abedi's 18-year-old friend that caused him to kill.
Abdul Wahab Hafidah was run over and stabbed in Manchester in May 2016 in what is believed to have been a gangland killing.
An unnamed family friend said Abedi was 'vowing revenge' at the funeral and he viewed the murder as a hate crime.
They added that Abedi became increasingly religious and interested in extremist groups.
Before his arrest in Tripoli yesterday, Abedi's father said his son had been affected by the death.
He told the New York Times: "Yes, a friend of his was killed by the gangs of Manchester, but that doesn't mean that he carried out an attack for it."
Ramadan Abedi, was arrested by masked gunmen in Tripoli while recording TV interviews in the country.
He had claimed his son seemed "normal" when they spoke five days ago and insisted: "We don't believe in killing innocents."
Abedi's younger brother Hashem has also been arrested in Libya, on suspicion of having links to ISIS, who claimed responsibility for Monday night's atrocity.
He was "aware of all the details" of his brother's plans, a Libyan security force official said and had been "under surveillance for a month and a half" before his arrest today.
The Deterrence Force said on its Facebook page that "investigation teams supplied intelligence that he was planning a terrorist attack in the capital Tripoli".
Abedi's older brother Ismail, 23, was arrested on Tuesday in Chorlton, south Manchester.
His uncle was detained yesterday in Manchester, while there are conflicting reports that the killer's mother is also in police custody.
Attention has been focused on how the bomber had been allowed to slip through the net and why warnings about his descent into jihadism were apparently overlooked, the Daily Mail reported.
Yesterday it was alleged that two calls about his conduct had been made to a police anti-terror hotline and that his family had repeatedly raised concerns he was "dangerous".
It was also claimed the Salford university drop-out had travelled extensively in the Middle East and received terror training in Syria.
He is believed to have returned to the UK from Libya just days before the attack.
It has also emerged that detectives were probing possible links between the Manchester Arena atrocity and the Paris and Brussels terror attacks.
Sources said officers are exploring whether the same cell was responsible for all three outrages.