International show jumper and Olympic mount Wonderboy III has died, most likely from a cardiac condition leading to aortic rupture, according to his owner.

The 14-year-old gray Belgian Warmblood gelding collapsed under saddle Jan. 7, said Georgie Crumley of Crumley Equestrian Group in Alfold (Surry), U.K.

"I was cantering on the gallops with him when he suddenly felt exhausted," Crumley said. "I immediately brought him back to walk where he felt very wobbly, so I jumped off of him. As soon as my feet touched the ground, he collapsed."

The horse had had some performance issues recently, often underperforming after two days of competition, according to Crumley. "His third day was terrible, just like he was so empty," she said. "I do know that some horses have off days, but that just was not the sort of horse he was."

Veterinary evaluations at the time were inconclusive, Crumley said. Although no necropsy was performed, Crumley said the likely posthumous diagnosis was probable aortic weakness, ending in rupture.

Attending veterinary hospital Kings Park Equine Clinic in West Sussex declined to comment, citing privacy concerns.

Wonderboy III won the Rolex Grand Prix show jumping title in Zurich, Switzerland, in January 2010 under then-owner/rider Ben Maher. The horse competed in the 2012 Olympics in London under his new owner and rider, Ahmad Saber Hamcho of Syria. The pair finished in 62nd place individually.

Crumley had just bought "Basil" back in September 2012, after having sold him to Maher in 2008.

"When we actually went to collect him in September,