A 17-year-old amateur boxer died shortly after collapsing in the ring during a tournament fight.
The teenager, named locally as Ed Bilbey, was given medical treatment at the match on Friday night in South Normanton, Derbyshire, but was pronounced dead in hospital.
Friends have described how the "cracking lad", from nearby Ripley, fought like a "bloody trooper" and how his family were by his side "until the end".
Police say there do not appear to be suspicious circumstances but are asking anyone with footage of the fight to get in contact.
"Even though he was younger than everyone else he had one of the biggest hearts in the gym," said friend Mehdi Asghari, 27, speaking to The Telegraph, who met him at his local Shinfield's gym.
"As a boxer he was very talented, with big ambition. He always strived to be the best, instead of doing what normal kids his age would. He was always trying to be one of the best boxers who ever lived.
"Ever since I met him, every time I saw him, he always had the brightest smile on his face, a smile so bright that it would light up the neighbourhood."
A Facebook post from Ed's club, Somercotes Elite Boxing Academy, wrote a good luck message on Friday morning both for Ed and his brother Henry Bilbey.
It said the contest, with Earl Shilton Amateur Boxing Club, for the East Midlands Challenge Belt, "promises to be explosive".
Ady Corssen, who described Ed as a "cracking lad", also wrote: "[I] couldn't believe this was happening. You feel so helpless but have to let the professionals do their best to save lives. Seeing Ed lying there is something I will never forget.
"I can't even imagine what his opponent from last night is feeling. Thoughts go out to all his family and everyone this has affected."
Lisa Hobson said: "I'd just like to say that Ed Bilbey boxed like a bloody trooper last night and was with him and his mum and family till the end last night. I can't believe the night ended like it did."
Derbyshire Police said they were called to the Post Mill Centre, in South Normanton, at 10.17pm, before he was pronounced dead on arrival at Kings Mill Hospital in Mansfield, Nottinghamshire.
Formal identification has yet to take place and a post-mortem examination is due to be carried out to establish the cause of death.
Police have appealed for anyone with footage of the bout to contact the investigations team.
A force spokesman said: "At this stage there don't appear to be any suspicious circumstances surrounding this death but if you were at the tournament and have any footage of the bout or information that might help, please contact Detective Sergeant Debbie Yoxall on 101, quoting incident number 1162 of March 24."
Earlier this month, 14-year-old kickboxer Scott Marsden died two days after collapsing during a national title fight competition in Leeds.