Odanis Acuna, an exercise rider for trainer Kenny McPeek, suffered fatal injuries early Saturday at Churchill Downs when the horse he was breezing before dawn broke down in both front legs. Acuna incurred head and neck injuries that proved fatal, said McPeek, who was en route from Lexington to Louisville in the aftermath of the accident.

Acuna, a 42-year-old native of Cuba, had worked for McPeek for about 10 years. He also worked for a local horse-feed company.

"Obviously everyone is extremely upset about this," he said. "Odanis was a fantastic person and one of the hardest-working people you'll ever meet. It's a real tragedy."

The horse was New York Harbor, an unstarted 2-year-old Verrazano colt who had to be euthanized, said McPeek.

In the wake of Acuna's death, training at Churchill was canceled for the rest of the morning following the 7 a.m. Eastern harrow break.

Further details will be made public when available. A Churchill spokesman said a statement will be issued later today.