Kain Parsons (37) died today after being injured in a match against Steve Alfeld during the Fight for Christchurch event at Horncastle Arena on Saturday night.
Parsons was not wearing headgear.
Inspector Darryl Sweeney said police were previously aware of the boxing match and are "liaising with the event organisers and officials to fully understand the circumstances surrounding his death".
"We are in contact with and extend our sympathies to Mr Parsons' family at this difficult time," he said.
"His death and all facts surrounding it will be referred to the coroner."
Parsons' family issued a statement through police this afternoon.
"The family of Kain Parsons wishes to advise that tragically he has succumbed to the brain injury he received at the Fight for Christchurch on Saturday 3 November," it said.
"We wish to acknowledge and thank the amazing team in the ICU ward at Christchurch Hospital, the paramedics at the event, along with the many doctors, nurses and medical professionals who left their tables to quickly come to Kain's aid.
"The outpouring of heartfelt support from family, friends, colleagues and the public has been humbling and very much appreciated.
"Kain gave his life in the pursuit of raising money for those less fortunate and his enormous heart, selfless attitude and gentle giant nature will leave a void in the lives of so many."
