Welsh boxer Dale Evans says he is "absolutely heartbroken" by the death of opponent Mike Towell.
Scot Towell, 25, died in hospital on Friday after being seriously injured in a fight with Evans the previous day.
He is the third professional boxer to die in the UK from fight-related injuries in the past 21 years.
"I feel like I am responsible," Evans, 24, told BBC Wales Sport. "I can't stop thinking about Mike and his poor family. All my thoughts are with them."
Towell was knocked down in the first round of the fight at Glasgow's Radisson Blu Hotel but recovered to continue.
Referee Victor Loughlin stopped the contest in the fifth round after Towell was knocked down for a second time.
He received treatment in the ring and was given oxygen before being taken to an ambulance on a stretcher.
In an emotional interview, Evans also said:
- He has felt "dreadful" since the fight;
- He has considered retiring from boxing;
- He would now like to win the British title in Towell's memory.
"It has been awful," he said. "All I can think of is his two-year-old kid and his girlfriend and family who won't have him around any more.
"I feel like I am responsible because we are the ones punching each other - and this is something I have to live with now."
Evans, who is trained by former world title challenger Gary Lockett, was stablemates with former British middleweight champion Nick Blackwell.
Blackwell's career was ended earlier this year when he suffered a bleed on the skull after losing his title to Chris Eubank Jr.
Lockett said the aftermath of that fight was the "worst time in my life".
"It is not about us 'going through this again', he told BBC Wales.
"We are only thinking about the Towell family and Mike's loved ones. Since the second the fight finished, all our thoughts have been with Mike's family."
Evans, who has won 12 of his 17 bouts as a professional, says boxers understand the risks involved in entering the ring but rarely consider the potential consequences.
"You don't think about this happening," he said.
"With the medical team at ringside you feel safe and you never actually dream something like this will happen. It isn't something on your mind."
St Clears boxer Evans is now the mandatory challenger for the British title but says he has considered retiring from the sport he loves.
"I have been low and thinking that I would probably stop boxing now, but I think I will have a break and I will try to win the British title in Mike's memory.
"I feel like one of my own family has passed away."
Towell's partner, Chloe Ross, said he died "peacefully" shortly after 23:00 BST on Friday, 12 hours after he was taken off life support.
"Michael had severe bleeding and swelling to his brain," she wrote on Facebook.
"He had been complaining of headaches for the last few weeks but we put it down to migraines with the stress of his fight.
"It has been the longest 24 hours of our lives. My baby has lost his daddy. But he will be so so proud of his dad in what he achieved."