A 22-year-old boxer is on life support in hospital after suffering a head injury in his first-ever bout.
Kuba Moczyk stepped into the ring for the first time at the Atlantis Arena in Great Yarmouth on Saturday, having trained for months in preparation for the big day.
In the first two rounds, observers said he looked to have the better of his opponent. However, in round three he was caught by a solid punch which knocked him over.
The fight was ended at that point and Mr Moczyk was rushed to the James Paget University Hospital at Gorleston at about 9pm.
The factory worker is now in intensive care at the hospital, with twin sister Magdalena by his side, pleading for him to wake up.
Miss Moczyk, who is five minutes younger than her brother, said: 'He may have wanted to be a boxer, but he is just the kindest and gentlest man - we are very close.
'He had been training for a long time and it was his dream, but he is not the kind of person to want to hurt anybody. All he wanted to do was show what he could do and make his team proud.'
Mr Moczyk had spent more than four months training for his big debut, and was excited heading into the bout, Miss Moczyk said.
She added: 'We are refusing to let go of him.'
The fighter had been training for the unlicensed event at Lenny Boy's Gym in Yarmouth and his trainer, Scott Osinski, said all the right medical preparations had been carried out before the fight.
Mr Osinski said: 'It was such a shock, he was all smiles in between the rounds and enjoying himself, but it was just a freak blow of nature.
'Everybody at the club is pulling for him, he is like a brother and a friend to us all. My message to him would be to keep fighting - we all love him and his health is our only concern.'
The event was organised by promoter Aurelijus Keree, who said he was 'deeply saddened' by what had happened.
A spokesman for Mr Keree said: 'Aurelijus's thoughts are with Kuba and his family at this time. He hopes he will make a full recovery.'
Mr Keree said correct health and safety measures were followed.
Leading Great Yarmouth boxing promoter Leon Docwra said the incident had sent 'shockwaves throughout the boxing world'.
Mr Docwra, who was not involved with organising the event, said: 'I cannot believe what happened. Kuba is a really nice kid who is very close with his family.'
James Paget's medical director Nick Oligbo said: 'We are liaising closely with the family and understand how difficult this situation is for them.'
A fundraising page has been set up for people wanting to support the family, and raised more than £3,000 in its first 24 hours.
Police have today confirmed the incident is not being investigated.
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