MIAMI -- A horse was found killed and mutilated on a rural Miami-Dade County road Sunday morning, and several similar horse killings have been reported in recent months.

Andrew Ortiz, 16, came across the scene of the slaughter near 154th Street and Southwest 212th Avenue Sunday morning while he was riding his ATV. Ortiz, who has horses himself, said the sight nearly made him sick.

"It was mutilated. They cut three legs off, stabbed it and left it right there, tied it to a tree. Nasty people -- very nasty people," Ortiz said.

"Horse slaughter in South Florida is escalating. It is on the rise," said Richard Couto, an investigator for the Society for the Prevention of Cruelty to Animals. "In the last 30 days alone, there have been five reports of horse slaughter."

In May, two horses were found slaughtered in Broward County, as well.

Investigators said they believe the killers are harvesting the horses' meat and selling it on the black market.

"This meat is toxic. These are pets being stolen. These horses are seeing monthly treatments from a vet, being injected by numerous drugs," Couto said.

The meat can fetch up to $20 per pound.

In the most recent killing, police think whoever slaughtered the horse Saturday night might have been spooked and didn't finish the job.

Horse owners across South Florida are talking about the killings, and many said they are worried about turning their horses out at night. However, they said keeping their horses in their stalls 24 hours a day is not an option.

"It's terrifying. Luckily, my bedroom window looks right out to the pasture so I can open up my bedroom window and look at them. But I certainly will do that more often now," said horse owner Pam Weiner.

Killing horses is a crime, as is selling horse meat. Police continue to search for the killers.