Every race car driver heads onto the track understanding this race could be the last and hoping it won't be.
On Sunday, IndyCar drivers got a harsh reminder when the worst happened to one of their own.
Two-time Indianapolis 500 winner Dan Wheldon died when his car got caught up in a 15-car pileup, sailed over another vehicle and smashed into a catch fence at IndyCar's season-ending race at Las Vegas Motor Speedway.
''Things happen in this kind of racing,'' said Wade Cunningham, also caught up in the wreck. ''It's so close. Not much room for error. I was near the front of what caused all this, so I'm not thrilled about it. At this point, whose fault it was is kind of immaterial.''
The green flag had barely stopped waving when disaster struck.
Wheldon, driving from the back of the field for a chance at $5 million, was moving through the pack when he drove into a tangle of cars careening off each other in every direction.
Unable to avoid the massive wreck unfolding before him, Wheldon clipped another car and went hurtling through the air, his car bursting into flames as it flew into a fence.
After just 11 laps, the race was over. Two hours later, track officials announced that Wheldon was dead. The Englishman was 33.
''One minute you're joking around at driver intros and the next, Dan's gone,'' said Dario Franchitti, whose wife, actress Ashley Judd, had to bring him a box of tissues. ''I lost, we lost, a good friend. Everybody in the IndyCar series considered him a friend. He was such a good guy. He was a charmer.''
With the speed - close to 225 mph during practice - and a crowded 34-car field, a big worry was aggressive driving early in the 200-lap race.
Chaos started when two cars touched tires coming around turn 2 and almost no one had time to react.
Within seconds, several cars burst into flames and debris covered the track nearly halfway up the straightaway. Some points of impact were so devastating workers had to patch holes in the asphalt.
Video replays showed Wheldon's car turning over as it went airborne and sailed into what's called the catch fence, which sits over a barrier designed to give a bit when cars make contact. Rescue workers were at Wheldon's car quickly, some furiously waving for more help to get to the scene.
''It's unfortunate that early on in the race they've got to be racing so close. ...,'' Team Penske owner Roger Penske said. ''You always worry about those at these mile-and-a-halves at the speed and with this many cars.''
Three other drivers, including championship contender Will Power, were hurt in the pileup.
Wheldon was airlifted from the track to University Medical Center; news of his death came from IndyCar CEO Randy Bernard:
''IndyCar is very sad to announce that Dan Wheldon has passed away from unsurvivable injuries,'' he said. ''Our thoughts and prayers are with his family today. IndyCar, its drivers and owners, have decided to end the race.''
In his honor, drivers, many sobbing openly, took part in a five-lap salute around the 1.5-mile oval as thousands of fans stood and cheered from the grandstand.
Also injured in the crash were JR Hildebrand and Pippa Mann. Both will remain in the hospital overnight. IndyCar said Mann was being treated for a burn to her right pinkie finger and will be released Monday morning; Hildebrand was awake and alert but will be held overnight for further evaluation. Power was evaluated and released.
An autopsy was planned Monday for Wheldon.
''I'll tell you, I've never seen anything like it,'' Ryan Briscoe said. ''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 with no car attached to it and just debris everywhere. So it was scary, and your first thoughts are hoping that no one is hurt because there's just stuff everywhere. Crazy.''
IndyCar has not had a fatality since Paul Dana was killed at Homestead in 2006 during a crash in a morning warmup. Wheldon won the race later that day.
The accident appeared to start when Cunningham's car swerved on the track and Hildebrand drove over the left rear of Cunningham's car. Hildebrand appeared to go airborne, and Cunningham's car shot up into the wall, setting off a chain reaction among the cars behind him.
Some of those cars slowed, others didn't, and others spun in front of Wheldon and Power. There was so much confusion on the track it was hard to tell who was driving what car.
Power appeared to fly over Alex Lloyd's car, his ride rolling into the catch fence and landing on its right side. His in-car camera showed one of the front tires coming toward him in the cockpit.
Wheldon then appeared to drive over a car driven by Paul Tracy, who seemed to be slowing down. Wheldon, however, went airborne and spun into the fence.
''It was like a movie scene which they try to make as gnarly as possible,'' said Danica Patrick, making her final IndyCar start. ''It was debris everywhere across the whole track. You could smell the smoke. You could see the billowing smoke on the back straight from the car. There was a chunk of fire that we were driving around. You could see cars scattered.''
Wheldon, who came to the United States from England in 1999, won 16 times in his IndyCar career and was the series champion in 2005.
Despite winning this year's Indy 500, Wheldon couldn't put together a full-time ride this season but had a deal in the works for 2012.
Andretti Autosport, the team with which Wheldon won the 2005 Indy 500, had agreed to a contract early Sunday for Wheldon to replace Patrick next season. The deal was supposed to be signed after the race.
''Back when he was with the team in '05, we referred to the team as The Beatles because it was such perfect harmony (with his teammates) - and with Dan coming back, there was talk of putting The Beatles back together,'' said John Lopes, chief marketing officer and VP of marketing for Andretti Autosport. ''So today is devastating. We not only lost a future teammate, but a longtime teammate. It's so sad. He's going to be sorely missed and fondly remembered.''
Wheldon landed in the Las Vegas race thanks to Bernard's promise of $5 million to any moonlighting driver who could win the IndyCar season finale. Although there were no takers, Bernard refused to scrap the idea and Wheldon was declared eligible for the prize, which would have been split with a fan.
Asked about speed after the crash, Wheldon's former boss Chip Ganassi said, ''There'll be plenty of time in the offseason to talk about that. Now is not the time to talk about that.''
And Franchitti said: ''I agree. We'll discuss that and sort it out.''
But driver Oriol Servia didn't mince words: ''We all had a bad feeling about this place in particular just because of the high banking and how easy it was to go flat. And if you give us the opportunity, we are drivers and we try to go to the front. We race each other hard because that's what we do,'' he said. ''We knew it could happen, but it's just really sad.''
Wheldon had been providing blog posts for USA Today in the days leading up to the Las Vegas race, and in one posted Saturday to the newspaper's website he spoke of how he expected Sunday to be ''pure entertainment.''
''This is going to be an amazing show,'' Wheldon wrote. ''The two championship contenders, Dario Franchitti and Will Power, are starting right next to each other in the middle of the grid. Honestly, if I can be fast enough early in the race to be able to get up there and latch onto those two, it will be pure entertainment. It's going to be a pack race, and you never know how that's going to turn out.''
The accident spoiled what Bernard had hoped would be a showcase event for the struggling IndyCar Series.
The second-year CEO worked the entire season on turning the finale into a spectacle, and said he would offer his resignation to the IndyCar board of directors if ABC's broadcast didn't pull a .8 ranking. His goal was to improve upon last year's horrible television rating for the season finale and give the series some momentum for a strong season in 2013 with the introduction of a new car and new manufacturers.
So Bernard poured everything into Las Vegas, renting the speedway from owner Bruton Smith and agreeing to promote the event himself. He landed enough sponsorship to at least break even, and the $5 million challenge bought him an enormous amount of publicity the entire year.
Bernard got the Las Vegas Strip to close to stage a parade of cars, and hosted industry parties and a blackjack tournament to boost interest in the race. He even got MGM Grand Resorts to offer a pair of tickets to anyone staying this weekend in one of the chain's 14 properties.
But what was hoped to be a day of celebration quickly turned somber.
When drivers returned to the track for the tribute laps, Wheldon's No. 77 was the only one on the towering scoreboard. Franchitti sobbed uncontrollably as he got back into his car for the memorial ride. The sound of ''Danny Boy'' echoed around the track, followed by ''Amazing Grace.'' Hundreds of crew workers and representatives from each team stood at attention in honor of Wheldon.
''What can you say? We're going to miss him,'' Ganassi said. ''Everybody in IndyCar died a little today.''
AP Writer Ken Ritter in Las Vegas, AP Auto Racing Writer Jenna Fryer in Charlotte, N.C., and AP Sports Writer Tim Reynolds in Miami contributed to this report.