Scotland Yard has launched an urgent investigation in order to ascertain why the crush happened, amid reports that people without tickets had attempted to force their way inside.
Police were called to the venue shortly after 9pm following reports that large crowds were massing outside and that glass in the doors had been smashed.
Chief Superintendent Colin Wingrove, from the Met Police, said: “It is devastating news that a second person has lost their life following the events on Thursday. I wish to express my heartfelt condolences to Gaby’s family at this unimaginably difficult time.”
Detectives from the Met’s Specialist Crime Command are investigating the incident and are continuing to appeal for witnesses to contact them.
A Scotland Yard spokesman described the investigation as large and complex, and said officers were continuing to review CCTV and phone footage and speak to witnesses.
The spokesman added: “As with any police investigation, they will assess the evidence to establish whether any criminal offences were committed.”
In a statement published on Twitter, the O2 Academy expressed its “heartfelt condolences” to Mr Hutchinson’s family and friends.