MANCHESTER, England — Salman Abedi was wearing a red vest, his suicide bomb hidden in a small backpack, when he phoned his younger brother in Libya and asked him to put his mother on the line. It was about 10:20 p.m. on Monday, and the call was short.

“How are you doing, Mom? Please forgive me for anything I did wrong,” he said, and hung up.

A short time later, he walked through the glass doors of the Manchester Arena, the city’s biggest concert venue, lingered for a few minutes by the stalls selling merchandise related to Ariana Grande, the American singer who was performing there that night, and blew himself up, killing 22 people and wounding 116 more.

Since the attack, the police have taken 11 people into custody, and on Saturday Britain lowered its threat level from “critical” to “severe.” Officials are confident that they have captured the entire network. But the investigation continues into the network’s hierarchy, the precise logistics involved in planning the bombing, and what motivated Mr. Abedi.

The brief phone call to his mother — “forgive me for anything I did wrong” — encapsulated a deeply complicated family tale of conflict and rebellion, a complex interweaving of personal histories and the tortured recent history of Libya.