2:00 PM PT -- It has just been reported that the 23-year-old man who was taken into police custody after the tragedy is the bombing suspect's brother.

6:31 AM PT -- The suspected bomber has been identified as 22-year-old Salman Ramadan Abedi.

The suicide bomber at Ariana Grande's concert did not act alone ... according to police who say they've nabbed another man in connection with the attack.

Greater Manchester Police say they arrested the 23-year-old man Tuesday. They have not said what his connection is to the bomber, who was one of the 22 killed when he detonated the "nail bomb" Monday night in the rotunda at Manchester Arena.

The bust seems to point to the bomber not acting as a so-called lone wolf.

ISIS has claimed responsibility for the attack, claiming it was executed by one of its "soldiers."