Hart, 34, was being lowered to the ring on a guide wire when a harness carrying him released 15 metres (about 50 ft.) above the ground.

He fell, hitting his head on a turnbuckle.

Jim Bradbury, spokesman for the local fire department, said Hart was killed instantly by the fall, witnessed by 18,000 horrified fans at the sold-out event.

"He was up on some scaffolding above the ring. They were going to lower him down on some sort of cable and apparently, the cable wasn't hooked up," said Bradbury.

"He landed in the ring."

Bradbury said two paramedics working at the event rushed to the ring and started to perform CPR.

Hart was rushed to the nearby Truman Medical Centre in Kansas City, where doctors were unable to revive the wrestler.

He was pronounced dead a short time after arriving at the hospital.

The crowd at first thought it was all a stunt, then commentator Jim Ross repeated over and over to the audience that Hart's fall was not scripted.

Hart comes from a legendary family of wrestlers headed by his father Stu.

His brother, Bret, is a former WWF champion who now toils in the WCW. Owen was the youngest of 12 children.

Owen's wife Martha was struggling with the news her high school sweetheart, husband of 10 years and the father of their two children was dead.

"I'm just in such shock," she said. "I can't even believe it. I'm waiting for someone to call and say it's not true."

Martha said she, Owen, and their children Oje, 7, and Athena, 3, had "a perfect life" together and great plans for the future.

"He was just an outstanding person altogether -- the absolute best father on earth."

But Martha said she'd been fearful of Owen's Sunday stunt and had told him of her concerns before the event.

"I told him I didn't think he should do it. I didn't think it was safe. What would we do if anything happened to him?"

Owen's mom Helen also echoed that concern.

"I always worried about one of the boys getting crippled," she said last night.

"It's a dangerous sport in more ways than you can know. I just never thought one of my boys would be killed."

Stu Hart said Owen had performed the stunt with the wire before.

"Owen was a careful athlete who wouldn't have taken unnecessary risks or chances," Stu said.

Bret Hart was last night unaware of the tragedy as he was flying to Los Angeles to appear on the Tonight Show tomorrow.

Owen Hart was taking part in a World Wrestling Federation pay-per-view event called Over The Edge.

Ross, announcer for the WWF, stunned the North American wide TV audience when he revealed Hart's death.

"Tragedy befell the World Wrestling Federation and all of us," Ross said.

The accident also stunned wrestlers who went on with the show, at first unaware the accident was fatal.

Hart's last manager, Debra McMichael, was crying as she said: "Owen, we love you."

Hart -- who was wrestling as the Blue Blazer -- was scheduled to face off against the Godfather.

The Blazer was a superhero who told kids to "say prayers, eat vitamins and drink milk."

Hart joined the WWF in 1988 and had won several championship belts over the years.

It was a second tragedy for the WWF and the Hart family.

In October 1997, wrestler Brian Pillman, 35, was found dead in a hotel room in Bloomington, Minn.

Pillman had had problems with drugs.

And one year earlier, he'd spent a week in a coma after flipping his vehicle in Kentucky. Pillman was a close friend of the Harts who had been trained by the family.

Calgarian Ed Whalen, who worked with the Harts as an announcer for Stampede Wrestling, said Owen was a good man and completely devoted to his family.

"I've been with the Hart family for over 40 years, watching that kid grow up to become such an outstanding young citizen and athlete.