Witnesses told of nuts and bolts tearing into young music fans when the blast was detonated in the foyer area of the Manchester Arena moments after a concert by US popstar Ariana Grande ended. The bomb went off in a packed foyer area at a time when mothers and fathers were leaving the venue with their children and other parents were arriving to pick up groups of youngsters. Police this morning confirmed that the suicide bomber, who was known to police, died inside the arena. US security sources said the bomber had travelled to the venue on public transport. A 23-year-old man was arrested by anti-terror officers in the south of the city as police and security services attempt to work out if the suicide bomber was part of a cell.