For months, equestrian center workers were puzzled by a spate of injuries to horses and ponies in Delaware. It seemed someone was sneaking into the stables in the dead of night and tying up the animals’ back legs. Eventually police launched a sting operation to figure out who could have embarked on such a bizarre crime spree.

New Castle County Police officers never suspected how sordid their investigation would become.

On Thursday they charged Michael Riego, 31, of Hartly in Kent County, with two counts of felony bestiality and two counts of felony burglary in connection with the suspected serial rape of ponies dating back to September 2019. He is in jail pending $12,000 bail.

Authorities weren’t quite sure what to think when they first received reports about ponies and horses with injuries to their back legs at the New Castle County Carousel Park and Equestrian Center last fall. Some of the older horses exhibited clear discomfort and trouble walking related to circulatory issues from the tight leg restraints. Several of the smaller ponies, who are used to give riding lessons, were found with cords still tied above their back hooves.

Workers at the equestrian center took part in a video in February, asking for any help in cracking the case. Park director Mary Devine said that workers who discovered the first injured horse, a lesson pony named Sierra, “found it very disturbing” when they found her.

“The staff went over and they examined her and upon further evaluation, they discovered that she had cords tied around both fetlocks of her back legs,” Devine says in the video, referring to the hoof joints. “This is very, very upsetting that somebody would intentionally cause harm to any of our animals.”

After several more incidents police decided to set up a sting operation, installing hidden cameras throughout the barns in an attempt to find the culprit and uncover just what was happening to the animals and why their back legs were tied up.

On April 20, they received a call that a 31-year-old brown mare had been harmed overnight. Upon reviewing the surveillance footage from the evening before, they discovered a man wearing a dark jacket entering the stall around midnight with a bucket of grain. He then tied up the mare’s back hooves; pulled down his pants and sexually assaulted the horse, which writhed in pain from the leg restraints though did not seem to notice the penetration. After ejaculating into the horse, the man got dressed and left the stall, taking the bucket of grain with him.

The man’s face was covered, so authorities were not able to identify him. They further enhanced their electronic surveillance equipment and began nightly watches of the pony stalls, according to a post on their Facebook page.

On May 21, they witnessed what they believed to be the same man carrying a feed bucket checking out various pony stalls around 12:30 a.m. Once he identified his next victim, detectives watched him tie up the pony’s back legs.

They entered the stable to find Riego crouching in the corner with his zipper undone. He is alleged to have been the sole perpetrator of all the assaults.

Police say the investigation is still ongoing to determine if Riego assaulted other area horses. The injured ponies have all resumed normal daily activities.