They already did mate, one example:

Manchester Arena suicide bombing, on 22 May 2017, killed 22 concert-goers and parents who were in the entrance waiting to pick up their children following the show and injured 1,017.

Abedi made his final journey towards the City Room at 9:29 p.m., arriving at 9:33 p.m. Abedi was spotted by a person who was hired to prevent illegal screen recordings of the concert—by 10:00 p.m. She said that she had informed a BTP constable of Abedi's presence.

Abedi was spotted again at 10:12 p.m. by another member of the public, who asked what he had in his bag. He was concerned that the bag may have contained a bomb after he did not answer, and reported him, and was told that the BTP were already aware of Abedi. After being told of the concerns, a Showsec employee was afraid that he would be considered a racist and did not approach Abedi. While he attempted to get through on the radio, heavy radio traffic prevented him from reaching any other people. As the concert ended, concert-goers left through the City Room, one of four entrances into the arena. At 10:30 p.m., Abedi descended from the mezzanine.

At exactly 10:31 p.m. (21:31 UTC), the nail bomb, weighing in excess of 30 kilograms (66 lb), detonated in the City Room.

They already did mate, one example:

Manchester Arena suicide bombing, on 22 May 2017, killed 22 concert-goers and parents who were in the entrance waiting to pick up their children following the show and injured 1,017.