Lots of dead at the exit foyer where concert goers always pack up when leaving. Ideal kill zone for IED. This was planned.
From The Sun:
https://www.thesun.co.uk/news/3624815/manchester-arena-explosion-ariana-grande-gig-multiple-deaths/
Chris Parker, 33, was walking through the station towards the box office when one explosion went off.
He said he saw at least six people seriously injured on the floor and told the Sun: “I was walking through and one huge bang went off.
“There was nuts and bolts flying everywhere, and also human flesh. It was just one bang and a white flash. I treated a woman called Pauline. I’ve got blood on my hands. It was like a war zone inside where the box office is.
“There looked to be at least six people potentially fatally wounded. I saw one woman’s leg off. It is mayhem.”