A helicopter carrying the owner of Leicester City FC crashed in flames near the club's ground, killing five people.
The club confirmed its owner, Vichai Srivaddhanaprabha, was among those killed, along with two members of his staff, another passenger, and the pilot.
Here is what we know so far about the crash.
The helicopter took off from the King Power Stadium at about 20:30 BST on Saturday, as it often does after Leicester City games.
BT Sport cameras captured the take-off on live TV, as presenter Jake Humphrey watched and commented on it with pundits Owen Hargreaves, Chris Sutton and John Hartson.
A bang was heard shortly after as the helicopter spiralled out of control and crashed near a car park.
Former Leicester City and England goalkeeper Peter Shilton witnessed the crash when he was coming out of the ground with his wife.
"We saw the chairman's helicopter above us and all of a sudden it seemed to be making a funny noise and started to spin," he said.
"All of a sudden it started coming towards us and my wife started panicking.
"It seemed to drop a little bit and then obviously crash.
"Then there were sparks coming out the back and then some small flames, and then larger flames, I mean this all happened very quickly, and then suddenly it just blew up."
Freelance photographer Ryan Brown had been at the match covering the game.
"I heard the helicopter take off," he told BBC Radio 5 Live. "I turned around and it made a whirring noise and grinding noise and then went silent, it was spinning out of control.
"The blades had stopped spinning and then there was a big bang and a big fireball. Lots of people started running towards the scene; as I came around the corner there was a huge fireball.
"It crashed right near the stadium. It just cleared the stadium roof and landed in an industrial park next to it."
Who was on board the helicopter?
Vichai Srivaddhanaprabha, 60, was a billionaire and founder of duty-free consortium King Power International.
He bought Leicester City in 2010 and the club went on to win the Premier League title in 2015-16 in one of the greatest sporting surprises of all time.
The father-of-four was ranked as the fifth richest person in Thailand by Forbes Magazine.
He used to fly to and from Leicester's home games and his properties in London and Berkshire, landing his helicopter on the pitch.
Two members of his staff, Nusara Suknamai and Kaveporn Punpare, were with him on his final flight.
Ms Nusara was a former model who was runner-up in Miss Thailand Universe 2005, and was voted most photogenic in the same contest.
Little is known about Mr Kaveporn but his Facebook page said he was from Bangkok.
The helicopter's pilot, Eric Swaffer, had more than 20 years of flying experience as a private jet and helicopter pilot, flying helicopters for live media broadcasting including Channel 4's The Big Breakfast.
He lived in Surrey with his partner Izabela Roza Lechowicz, who died alongside him in the crash.
Ms Lechowicz moved to the UK from Poland in 1997 and became a pilot after meeting Mr Swaffer.
She was a winner of the #polka100 award, an accolade for "exceptional women who inspire the Polish community in Britain".
How did the crash happen?
An investigation into the crash is being led by the Air Accidents Investigation Branch (AAIB), which investigates civil aircraft accidents across the UK.
The investigation will look into how the Agusta Westland AW169 helicopter crashed in what is believed to be the first accident involving an AW169 aircraft.
The owners have two helicopters - an older one registered as G-LCFC and a newer one registered as G-VSKP.
The helicopter that landed at the stadium was the G-VSKP.
Jim Rowlands, a former RAF Puma crew member, said the spinning nature of the aircraft indicated there was a problem with the tail rotor - the part of a helicopter that normally stops it from spinning around in the opposite direction to the main rotor blades.
"If you lose your tail rotor it's almost impossible to recover from," said Mr Rowlands.
"You can't get out of it. It would be more luck than judgment if you were to survive."
His "gut feeling" was there was some kind of mechanical problem but said there were "so many things that it could have been".
"It could have been a human factor, it could have been pilot error or poor maintenance that led to something," he said.
An AAIB spokesman said: "A team from the AAIB has been deployed to the site and is investigating.
"Anyone with information that might be helpful to the investigation is asked to contact the police."
How have people reacted?
The Duke of Cambridge led the tributes to Mr Vichai on Monday, saying he was lucky to have known him for several years.
"He was a businessman of strong values who was dedicated to his family and who supported a number of important charitable causes," Prince William, who is president of the FA, said.
"He made such a big contribution to football, not least through Leicester City's magical 2016 season that captured the imagination of the world."
Former Leicester City and England striker Gary Lineker tweeted to say he was "deeply saddened" to hear of Mr Vichai's death. He signed off the Match of the Day programme on Saturday by saying it had been a "dreadful day".
Deeply saddened to hear the confirmation that lcfc chairman, Vichai Srivaddhanaprabha was one of 5 people to lose their lives in the helicopter crash on Saturday evening. A quiet,… https://t.co/FeTlx2ldq8— Gary Lineker (@GaryLineker) October 29, 2018
Speaking outside the stadium, club ambassador Alan Birchenall said Leicester City owed "everything" to Mr Vichai.
"I had to pay my respects to a lovely guy," he said. "We owe everything to him. We wouldn't have won it [the Premier League] without him. We wouldn't have got near it without him.
"There won't be a dry eye among any of the staff today."
Mr Swaffer's friend Lucie Morris-Marr said the pilot was a "veteran in the field" and would have done all he could to prevent lives being lost in the crash.
She described him as a "funny and vivacious" man who was in an "aviation love story" with Ms Lechowicz.
The couple were professional pilots who lived together in Camberley, Surrey. Ms Lechowicz moved to the UK from Poland in 1997.
In a statement, the Polish embassy said: "She [Mrs Lechowicz] was a great pilot, winner of the #Polka100 contest. It contributed to the creation of a positive image of Poland in the UK."
Prime Minister Theresa May said: "The outpouring of grief is a testament to how many people's lives were touched by those on board."
How do fans feel?
Season ticket holder Richard Jackson, of Market Bosworth, said he was "devastated" by what had happened.
"These owners have been absolutely fantastic; probably the best owners in the whole English system," he said.
One fan said of the family: "They are the heart and soul of Leicester City Football Club.
"If it wasn't for them none of this would have been possible in recent years and dreams wouldn't have come true.
"It's very disturbing, not just for fans of the club but for everyone in the football world."
Richard Mobbs, from Burton Overy in Leicestershire, said he last saw the chairman in June when they discussed a player who was about to join the club.
Mr Mobbs described Mr Srivaddhanaprabha as a "lovely, quiet, down to earth man", and paid tribute to his family.
Anupat Maturongpituck, a student from Thailand studying at the University of Leicester, came to the King Power Stadium on Sunday to "pay my respects", adding news of the crash has had a "great impact" in Thailand.
Mr Vichai has regularly given supporters free beer and pies at matches to mark special occasions, made donations to the city hospital, and treated the 2016 title-winning squad to a fleet of blue BMWs.
Another fan said: "It's ended up as probably the darkest day in Leicester City Football Club's history."