WESTERLO — Shawn M. Duncan was arrested in connection with the death of his father’s beloved thoroughbred horse, found on Sunday morning with an arrow in its side.

“Whenever you walked up to the fence, Belle was the first to greet you, and we think that’s what cost her her life,” Shawn Duncan’s stepmother, Lorraine Duncan, said of the horse. She said she hopes Shawn Duncan didn’t shoot the arrow. She acknowledged there had been a disagreement between him and their family but declined to elaborate.

“He knows that his dad’s whole life are horses,” Lorraine Duncan said. “Unfortunately, I think he may be going through a difficult time.”

Robert Duncan competes in rodeos and has two other horses, his wife said. Belle was a racing thoroughbred. She was retired by a leg injury and would have been killed if they hadn’t taken her, she said.

“She became a very big part of our lives,” Lorraine Duncan said. “She’s a very gentle, loving horse.” Her daughter developed a fear of riding after being bucked off of another horse. Years later, her daughter started riding again with Belle, and was training on her for barrel racing.

“Belle is responsible for turning a lot of young people towards horses,” said Robert Duncan’s sister, Rosemary Filkins. “She was that sweet.” She said Belle was ridden in the procession for the Westerlo Fire Company’s 75th anniversary last year.

Duncan, 35, was sent to Albany County’s jail without bail, charged with third-degree criminal possession of a weapon, a Class D felony, and unlawful possession of marijuana, a violation, according to Albany County Sheriff Craig Apple.

Apple said a search warrant for Shawn Duncan’s Filkins Lane residence in Knox was issued in connection with the horse’s death; deputies found 15 grams of marijuana, bows and arrows, and a stun gun, which Duncan cannot have as a previously convicted felon. Apple would not give details of the evidence gathered to get the search warrant.

Duncan was not arrested for killing the horse. But if he were, he could potentially face additional charges, including animal cruelty and criminal mischief, Apple said, as the sheriff’s office continues to investigate the horse’s death.

“This is a clear indication of someone seeking revenge, and it’s clearly personal,” Apple said on Monday. “What drives somebody to this point, I don’t know. To me, it’s just a coward. They basically took frustration out on a helpless animal, a beautiful animal at that.”

Apple believes a compound bow or longbow was used to drive the arrow into the horse. He said it was a target arrow that entered 12 to 14 inches into the animal’s side.

“We miss her and, should they find the person that does this, we are going to prosecute to the fullest extent possible,” said Lorraine Duncan.

Of charges against her stepson, if he shot the horse, she said, “Yes, you have to really have some serious problems to do something like that to an animal. And that person needs a lot of help.”

After getting home at 10 on Saturday night, Robert Duncan went out to his pasture to check on Belle, Lorraine Duncan said. As she was getting ready for an auction in Greenville at about 8:30 a.m. on Sunday morning, Robert Duncan went to check on his horse again and found her dead.

Robert Duncan’s sister, Rosemary Filkins, came to see Belle once she heard. She said her hooves were compacted with mud, the arrow was broken off, and dirt around Belle’s body was loosened by her thrashing before she laid on the electric fence.

“The horse was in pain when she died,” said Filkins. “The horse suffered.”

Filkins said the pasture where Belle was found is in a back field and that her brother told her police took impressions of shoe and tire tracks at the scene.

Enterprise archives reveal some of Duncan’s history. He had been arrested in 2003, when the Albany County Sheriff’s Department found 37 marijuana plants in his Berne home. As a 17-year-old, he had been sentenced to two-and-two-thirds to five-and-one-third years in jail after he was arrested for burglarizing homes with others. When he was younger, Duncan participated in the Classy Hilltown Riders 4-H Club in East Berne and tae kwon do in Guilderland.