The images were of fire and smoke, of wreckage from terrifying, high-speed crashes.
Everyone wanted an explanation. There were only investigations and heartbreak — from Las Vegas to the Volga River.

Dan Wheldon, months after winning an improbable second title at the Indianapolis 500, died at 33 in an incendiary scene of carnage in the desert in the closing race of the IndyCar season.

The hockey club Lokomotiv Yaroslavl, one of the best in Russia and featuring former NHL players, plunged into a river bank soon after takeoff as it was about to begin a new season. All 37 players, coaches and staff died.

Sports lost a roster of greats in 2011: Joe Frazier in boxing, Duke Snider and Harmon Killebrew in baseball, Al Davis in football. Golf’s Seve Ballesteros and the marathon’s Grete Waitz never made it out of their 50s.

But the deaths of Wheldon and the entire Lokomotiv team — athletes on the job and in the primes — stood out as both sudden and shocking.

Wheldon was one of racing’s most popular drivers, an Englishman whose success never quite registered at home. And even though he already had won Indy in 2005, he had trouble getting rides this season because sponsors were hard to come by.

But there he was at the Brickyard in May, sailing to victory out of nowhere, the beneficiary of a rookie mistake by JR Hildebrand with one lap left.

“You never know what’s going to happen,” Wheldon said.

Less than five months later, his wisdom played out in the most chilling way possible.

Wheldon was well behind the leaders at Las Vegas Motor Speedway, but moving up. In an eye blink, he was caught in mayhem that would engulf nearly half the 34-car field. His car soared into the air and careened into a post in the fence surrounding the track.

The 19 cars that escaped that day later rode five laps in tribute. By year’s end, IndyCar said no one single factor was responsible for the accident, calling it a “perfect storm” of events.

The Lokomotiv team was on its way to Minsk for its opener in the Kontinental Hockey League, the world’s best after the NHL. But before the chartered jet reached full altitude, it smashed alongside a river and burst into flames. It was one of the worst air disasters in sports history. Investigators later cited lax oversight and insufficient crew training.

Three NHL players died in four months. Derek Boogaard, 28, a Rangers enforcer was found dead in his apartment and later determined to have a degenerative condition resulting from hits to the head. Another brawler, 27-year-old Rick Rypien of Winnipeg, battled depression. Recently retired Wade Belak, 35, was said to have hanged himself in Toronto.

Boxing sustained a big loss with the death of Frazier, 67, who spent his last days in hospice with liver disease. Smokin’ Joe was not big for a heavyweight, but how to measure his heart and grit? Or the ferocious power of his left hook? Or his sheer will in his three fights with Muhammad Ali? Promoter Bob Arum called him a “great, great warrior.”

Also gone from boxing in 2011 were heavyweights Ron Lyle, Scott LeDoux and knighted Englishman Henry Cooper. So were Gil Clancy, 88, the trainer who handled Emile Griffith, and Butch Lewis, 65, the promoter who went shirtless under his tuxedo and worked with Frazier and Ali, among others.

Davis was in command on pro football’s stage for more than a half-century and died at 82.

Football is now without four running backs who meant much to the game: Cookie Gilchrist, 75, a Bills star from Davis’ AFL days; Joe Perry, 84; John Henry Johnson, 81; and Ollie Matson, 80, once traded for nine players. Lee Roy Selmon, the defensive end who teamed with his brothers to help send Oklahoma to consecutive national championships before starring for the Tampa Bay Buccaneers, was 56. There were also a couple of ex-Giants in defensive end Andy Robustelli, 85, and kicker Don Chandler, 76.

John Mackey, stricken with dementia and dead at 69, was a force at tight end and later as players’ union president. Ex-Bears safety Dave Duerson was 50, turning a gun on himself, with his family agreeing to donate his brain for research. Orlando Brown, the 360-pounder who missed three seasons after a penalty flag struck him in the eye, died at 40. Bubba Smith, a fearsome 6-foot-7 pass rusher who later cut a more welcoming persona as an actor, was 66.

Baseball said goodbye to a couple of sluggers forever tied to their cities.

The 84-year-old Snider was “The Duke of Flatbush,” royalty of the highest order and one of Brooklyn’s “Boys of Summer.”

Killebrew, 74, was a balding brute of a hitter who personified the long-ball muscle of the 1960s. 

Baseball could field a strong team from its losses in 2011: Snider could be joined in the outfield by Jim Northrup, Gus Zernial and slap-hitting Matty Alou. Killebrew and Cardinals shortstop Marty Marion would do just fine on the left side of the infield, with George Crowe over at first base. Mike Flanagan, Woodie Fryman, Bob Forsch and Paul Splittorff would win some games on the mound, and bespectacled Ryne Duren might throw a few pitches against the screen to keep everyone honest. In the dugout would be a couple of managers with World Series rings: Dick Williams of the Athletics and Chuck Tanner of the Pirates, both 82.

In basketball, the clock ran out at 69 on Walt Hazzard, the outstanding point guard on John Wooden’s first championship team at UCLA; Dave Gavitt, 73, who helped create a Big East Conference now turned upside down; “Easy” Ed McCauley, 83, out of St. Louis and one of the NBA’s early stars; and Sherman White, 82, a breathtaking player for Long Island University who was jailed in the 1950s point-shaving scandal.

Lorenzo Charles died at 47, driving a charter bus on the highway. 

Ballesteros won five majors, but his place in golf was marked by more than championships. With a club in his hand, he was part genius, part daredevil, part entertainer. The Spaniard helped make European golf and the Ryder what they are today. Nick Faldo called him the “greatest show on earth.” Ballesteros had a brain tumor and was 54.

Waitz, too, left a stamp on her sport, taking the marathon to places it had never been. By the time she was done, this lean, blond Norwegian was practically a New Yorker as she glided through the boroughs. She won the city’s marathon there nine times, but she also won in London twice and on so many other courses around the world. She was her sport’s ambassador. Waitz, 57, fought cancer for six years, although she would never say what kind.

The bearded Socrates turned soccer into high art. He captained the Brazilian team at the 1982 World Cup, although it fell short of the title. He played with sophistication, commanding the field at all times.

He went on to become a doctor and always had much to say about his country’s politics. Drinking, however, got the better of him and he died at 57.

This year marked the end of a long run for Jack LaLanne, the fitness king who through his studios and TV show got millions of Americans off the sofa and moving again. He was said to have exercised every day of his life, and that’s a lot of days. He was 96.