British IndyCar driver Dan Wheldon has died following a massive accident at the Las Vegas Indy 300.
The Buckinghamshire-born star, 33, was one of 15 drivers involved in a crash at the second corner on lap 13 of the season-ending race.
Wheldon, who began IndyCar racing in 2002, was series champion in 2005 and won the Indy 500 in 2005 and 2011.
He had been without a permanent race seat this season but was bidding to win a $5m jackpot by winning in Las Vegas.
The accident at the oval-shaped track happened when a number of cars came into contact on turn two, sending several of them airborne, smashing into the outside wall and catch fence. The cars were traveling at speeds of over 200mph.
With cars burning and debris littering the track, the race was red-flagged.
It was the first-ever death at the circuit in its 40-year history.
Wheldon was airlifted to the nearby University Medical Center where he was joined by his family - including his wife Susie and two young sons Sebastian and Oliver - but his death was announced to his fellow drivers in a meeting back at the track.
On Monday, Clark County coroner Michael Murphy announced that autopsy results showed Wheldon was killed by blunt trauma to the head.
It was the first IndyCar fatality since 2006, when Paul Dana was killed during the warm-up for the season-opening Toyota Indy 300 at Homestead-Miami Speedway.
Wheldon had started the race at the back of the field and had made up 10 places in the first 12 laps before the crash.
IndyCar chief executive Randy Bernard said: "Our thoughts and prayers are with his family."
IndyCar bosses decided to end the Las Vegas race following the crash. Instead, the drivers took part in a five-lap salute, with Wheldon's number 77 the only number on the scoreboard.
Organisers also played the song Danny Boy, followed by Amazing Grace, as crew and mechanics stood around the track.
Wheldon, who was driving for Sam Schmidt Motorsports on Sunday, had failed to secure a regular ride this season after being replaced by JR Hildebrand at the Panther Racing team.
Despite that, Wheldon put together a deal with Bryan Herta Autosport for the Indianapolis 500, a race he ended up winning after Hildebrand crashed going into the final turn.
Wheldon then took up Bernard's offer to pay $5m (£3.1m) to any non-regular series driver who won the season finale at Las Vegas.
There were 34 cars entered in the Las Vegas race - one more entry than was the case at the far bigger Indianapolis 500 circuit.
Earlier in the week, drivers had voiced concerns about speeds of close to 225mph being reached at the track during practice.
"I'll tell you, I've never seen anything like it," said driver Ryan Briscoe.
"The debris we all had to drive through the lap later, it looked like a war scene from Terminator or something. I mean, there were just pieces of metal and car on fire in the middle of the track... just debris everywhere."
Former IndyCar and Formula 1 driver Mark Blundell was at the circuit and witnessed the accident.
"IndyCar racing is dangerous," he told the BBC. "The difference [between IndyCar and Formula 1] is that you are running four cars wide, only inches apart from each other doing 220mph.
"When there is a problem, it normally turns out to be a big problem because a small error can be quite costly."
The Briton also suggested the Las Vegas track was not big enough for the number of cars - 34 - that were competing on Sunday.
Consequently, when there is an accident it can, he said, result in "something quite catastrophic".
He added: "That's what you saw today - 15 cars out in one go and unfortunately the loss of Dan Wheldon, a guy who was a huge talent.
"He never quite got to the upper echelons of Formula 1 but was very well-known and very well-respected.
"He was a very accomplished driver who still had a huge career in front of him. It's big loss to British motorsport."
The scrapping of the race meant Scotland's Dario Franchitti secured a third straight series crown, as title rival Will Power was also caught up in the accident.
But Franchitti's only thoughts were for Wheldon and the 38-year-old was in tears in his car before setting off on the five-lap salute.
"Right now I'm numb and speechless. One minute you're joking around in driver intros and the next he's gone," said Franchitti.
"He was six years old when I first met him. He was this little kid and the next thing you know he was my team-mate.
"We put so much pressure on ourselves to win races and championships and today it doesn't matter."