This is from a story written in the Omaha World Herald this morning (Sunday):

High Limit slowed down noticeably while running sixth down the backstretch. Trainer Bobby Fankel found out after the race that both of the colt's hind legs had been stepped on. A replay seemed to show that Sun King caused the injuries when he ran up on the back of High Limit. Jockey Ramon Dominguez told Frankel after the race that the horse seemed uncomfortable. Dominguez let up on the colt down the backstretch and watched the remainder of the 20 horse field go past.
"We saw the trail of blood as we were wlking him back to the barn" assistant trainer Chad Brown said. "Ramon told us the horse seemed to be in pain, an we could see why."
The vet stopped at the Frankel barn after the race to inspect the colt. One hind leg was cut and the other had a deeper cut near the right hoof.
"With the injury he got, a horse will usually stop running as soon as it happens. That's what happened down the backstretch."
said Brown.