Mario Calderon was one of those semi-anonymous hard workers that make racetracks function. He had been a jockey for more than 30 years. Before he rode his final race at Philadelphia Park on Feb. 11, 2008, he wasn't getting many mounts, but was there in the morning, exercising horses, getting them ready for the races.

Calderon, 55, had just finished jogging 3-year-old Cassidy Blue early Sunday morning at Philadelphia Park when the horse, on the way back to the barn, apparently threw his head down toward the ground and pulled Calderon over. Calderon's boot got caught in one of the stirrups. He was dragged down the track and suffered devastating head injuries. He was taken by ambulance to a nearby hospital, but was soon pronounced dead.

Cassidy Blue was fairly new to the barn of longtime trainer Pam Shavelson, who had employed Calderon for approximately 15 years as an exercise rider.

"I didn't see the [accident] happen," Shavelson said. "I talked to two people who did see it."

After the horse threw his head, he "took off bucking," according to Shavelson. And there was nothing Calderon could do to protect himself.

"The way it happened, it was horrible." Shavelson said through her tears. "Everybody that saw it said it was the worst thing they ever saw."

Calderon began his riding career in Kentucky. In records going back to 1976, he rode in nearly 1,900 races, winning 221.

"I know a lot of people are going to try to help [Calderon's family]," Shavelson said.

Shavelson said Calderon, who lived in Croydon, leaves behind a wife and two young children, a boy and a girl.

"He can tell you a lot about horses," she said, still talking about her friend in the present tense. "He's a really good person, an unbelievable family man."