This is a terrible tragedy that feels especially close to home as my own kids often go to concerts there. It's not helpful at this stage to speculate on who carried out this attack but at this stage police are saying it was a single individual with a makeshift bomb. If this is the case, it's incredibly difficult to guard against: a lone actor who may have got details of bomb-making from the internet. Please let's not have an anti-Islamic backlash - I have Muslim friends who also often go to the Arena and I know they will condemn this insane act as wholeheartedly as the rest of us.