The owners of a dog that allegedly attacked and killed a miniature horse over the weekend have agreed to euthanize the animal, the Edgartown animal control officer told the town selectmen Monday.

Animal control officer Barbara Prada said Adam Mahoney visited Mugsy, a three-year-old neutered American Staffordshire-bulldog cross who is on 10-day quarantine at the pound Monday afternoon and “agreed they had to do the right thing and put Mugsy down,” she said.

When the state-mandated 10-day quarantine is up next Monday, Ms. Prada said, the dog will be put down. She said the owners will make arrangements with a veterinarian, and the dog will be brought to them for euthanizing.

The selectmen said they wanted to be sure the dog remained in quarantine or under the town’s control, and they voted 3-0 that the dog was dangerous and should not be released unless to the owner for euthanasia.

Magik, a miniature horse owned by Ellen Harley, was attacked and killed at the Harley farm of Meetinghouse Way sometime Saturday afternoon. Another miniature horse, Chance, was injured and is recovering.

A woman who had been feeding and caring for the horses found a gruesome scene in the paddock when she came to check on the animals; Ms. Prada said the animal that killed the horse cleared a four-foot split-rail fence that was lined with sheep fencing and was intact. She said there was no evidence that the horses had been chased or dragged down. Two other full-sized horses nearby were unharmed, she said.

“There were no bite marks on the horse [that was killed], the dog went right for the jugular, telling me the dog had done something like this before. It has to be a good-sized dog, or possibly dogs,” Ms. Prada said early Sunday when town authorities were still looking for the dog. She said the horse that was killed had most of its face ripped off. The injured horse had puncture wounds, was treated on the scene by its owner and remain in the paddock at the farm.

There were no known witnesses to the incident.

On Sunday, police received a tip about the identify of the dog that had attacked the horses, Ms. Prada said. Two dogs belonging to the Mahoneys, who live in Island Grove near the farm, “came home filthy and they had to give them a bath,” Ms. Prada said.

“I sort of thought of Mugsy at the time, but without proof didn’t want to go and accuse people,” Ms. Prada told the selectmen, noting that the dog had bitten a calf a year and a half ago.

The owners admitted that Mugsy came home with blood on him, Ms. Prada said. She added that she didn’t believe the second dog, a four-year-old neutered pointer cross, was involved. He is also on quarantine, though at the home of his owners.