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 son of Libyan parents, who reportedly fled their native country and sought refuge in the UK, he is thought to have come back to Britain from Libya just days before the massacre.
Here's everything we know about the 22-year-old Manchester Arena attacker.
What is his family background?
Born and raised in Manchester in 1994, Abedi, the second youngest of four children, grew up in a Muslim household but matured into a university dropout with an appetite for bloodshed.
His parents, mother Samia Tabbal and father Ramadan Abedi, a security officer, are Libyan-born refugees who fled to the UK to escape Gaddafi. It is thought they returned in 2011 following Gaddafi’s overthrow.
Abedi is thought to have an older brother Ismail Abedi, who was born in Westminster in 1993, a younger brother Hashim Abedi, and a sister Jomana, whose Facebook profile suggests she is from Tripoli and lives in Manchester.
A family friend, who asked not to be named, said the family 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 the Didsbury Mosque.
Sheikh Mohammad Saeed said he believed Abedi had displayed a "face of hate" after the imam gave a sermon denouncing terrorism.
Abedi went to Burnage Academy for Boys between 2009 and 2011, and then on to Salford University in 2014 where he studied business management before dropping out, according to a source.
This article continues at [UK Telegraph] Everything we know about Manchester suicide bomber Salman Abedi