Manchester attack: Timeline of Salman Abedi's actions that led to concert terrorism

This image shows people running through Manchester Victoria station after an explosion at Manchester Arena. in Manchester England, Monday May 22, 2017. An apparent suicide bomber set off an improvised explosive device that killed over a dozen people at the end of an Ariana Grande concert. (AP)

British police said Salman Abedi, 22, of Manchester, carried out a bombing attack at an Ariana Grande concert that left at least 22 people dead and 119 others injured.

So far, eight people are in custody and held on suspicions of offenses violating the Terrorism Act. Among the detained are Abedi’s two brothers, Hashim and Ismail, as well as his father, Ramadan.

A British law enforcement official told Fox News that they feel they are reaching the “outer edge” of the circle of helpers, a network that supported Abedi and his attack.

MANCHESTER ATTACK: HUNT FOR POSSIBLE 2ND BOMB UNDER WAY

Britain’s security level was upgraded to “critical,” meaning officials believe another attack could be imminent. On Friday, reports said there may be a second explosive device.

Here's what we know about the timeline of the events leading up to the Manchester terror attack:

2015

• Abedi angrily responded to an imam at Didsbury Mosque during his sermon that was reportedly anti-Islamic State. Abedi was reportedly banned from the mosque. This is the first public sign of the suicide bomber’s radicalization.

May 2016

• A British Libyan friend of Abedi’s was killed in a car accident. Abedi believed the accident was a hate crime. Sometime later, he opened a bank account which he did not use until he bought items related to the attack.

March-April 2017

British police identified Salman Abedi, 22, as the bomber responsible for Monday’s explosion at the Manchester arena which killed at least 22 people. (AP)

• Abedi purchased items in B & O Garden and Home Store. It’s possible to buy fertilizer chemicals that can be used in a home-made bomb. He also purchased some items at ScrewFix hardware store. Nuts and bolts used as shrapnel were found at the scene of the bombing.

Approximately April 27

• Abedi left Britain to visit Libya for three weeks. His father, Ramadan, and brother, Hashim, live there. Some believe the suicide bomber received training on how to build a bomb during his stay.

Thursday, May 18

• Abedi returned home from Libya via Istanbul and Dusseldorf. Investigators are looking into whether he was given bomb-making material in the German layover.

Friday, May 19

• Abedi was seen at a shopping mall a few blocks from the Manchester Arena. He bought a backpack used in the attack.

Weekend May 20-21

• It is reported that Abedi put together his explosive device at his home, located three and half miles from the arena. There were chemicals found at the residence.

Monday, May 22

• Abedi relocates to a rented apartment near the bombing site to put together the final touches to his homemade bomb. There were traces of chemicals found at the residence.

Later Monday, May 22

• Abedi blew himself up at the arena, killing at least 22 people and injuring scores of others.