Just after 10.30pm on 22 May 2017, as more than 14,000 people were leaving a performance by American pop singer Ariana Grande, an improvised explosive device was detonated in the foyer of the Manchester Arena. The detonation killed 23 people and injured another 250. One of those killed was the suicide bomber, Salman Ramadan Abedi. There was then-and indeed continues to be-some confusion about the extent to which the UK authorities were aware of Abedi's activities prior to the bombing. He had been arrested in 2012 for minor criminal offences. The British Broadcasting Corporation (BBC) also reported that acquaintances of Abedi at Manchester College had called an anti-terrorism hotline expressing concern about his extremist views. Any knowledge of these calls was denied by the Greater Manchester Police; however, the UK's domestic intelligence agency, MI5, has since commenced a review of its processes in light of confirmation by the callers. An independent report of MI5 and police internal reviews was also released in December 2017. This report, by former Independent Reviewer of Terrorism Legislation (IRTL) David Anderson, clarified that while Abedi was a peripheral subject of interest, he was not under investigation at the time of the attack. He was classed as a 'closed' subject of interest of 'low residual risk', meaning he was no longer assessed as representing a national security threat. However, Abedi had also recently been identified as one of a 'small number of individuals ... who merited further examination'. This further examination as to the threat posed by Abedi was due to take place on 31 May 2017, a mere nine days after the Manchester Arena terrorist attack.