A dog that is believed to have killed a miniature horse and injured another Saturday is under quarantine at the Edgartown pound, animal control officer Barbara Prada said early Sunday afternoon.

The two miniature horses were attacked at the Meetinghouse Way Farm owned by Ellen Harley sometime Saturday afternoon. Magik, Ms. Harley's horse, was killed, while Chance, owned by Kirsten Davey, was injured and recovering Sunday.

Ms. Prada said a tip led the Edgartown police department to the dog owned by Adam Mahoney of Island Grove. The Mahoneys confirmed that their dog Mugsy, a three-year-old neutered American Staffordshire-bulldog cross, had been on the loose Saturday and had returned home bloody and muddy and covered with scratches. Ms Prada said the owners are cooperating fully with the police and animal control department. “The owners feel terrible and they had no idea,” Ms. Prada said.

A second dog, a four-year-old neutered pointer cross also owned by the Mahoneys, was on the loose as well on Saturday, but Ms. Prada said the dog had no scratches and was not bloody and was likely not involved in the incident. The Mahoneys now face a choice of whether to have the dog put down, Ms. Prada said. “We talked about it and the owners are going to think about it,” she said. If the owners do not decide to put the dog down, the owner of the horse may press charges, in which case the matter would be referred to the selectmen and Ms. Prada would be asked to make a recommendation.

Early Sunday, Ms. Prada and police were looking for a large dog or possibly pack of dogs in the Meetinghouse Way area of town following the incident.

Ms. Prada said the miniature horse was killed sometime between 11 a.m. and 4:30 p.m. on the Harley farm.

Ms. Prada’s assistant, Jamie Pience-Riley, was on duty and called her when she was received the report late Saturday afternoon. A woman who had been feeding and caring for the horses found a gruesome scene in the paddock with one miniature horse dead and another injured.

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. 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 was recovering at the farm Sunday.

There were no known witnesses to the incident.

Ms. Prada said by protocol she called an Edgartown police officer and the chairman of the board of selectmen to the scene as witnesses. Board chairman Margaret Serpa and Edgartown police officer William Bishop responded.

“Honestly it was probably the most horrific animal complaint call I have responded to,” Officer Bishop said Sunday morning.

Farm owners in the Meetinghouse Way area, a rural area on the outskirts of Edgartown that reaches down to the Edgartown Great Pond, were notified to be extra vigilant in minding their livestock.

Before Mugsy was found, there was some speculation about whether a coyote was responsible. Ms. Prada thought this was highly unlikely, and Augustus (Gus) Ben David 2nd of Edgartown, a noted Vineyard authority on wildlife biology who has carefully tracked a small handful of coyote sightings on the Vineyard in the past two years, concurred.

“I can tell you on very firm biological grounds that this is not a coyote kill,” Mr. Ben David said Sunday morning. “We haven’t had a reliable coyote sighting in well over a year, and this is an atypical situation. If we did have coyotes here, at this time of year there is a plethora of wildlife for them to eat,” he said. He also noted that the small handful of sightings were on the remote north shore area of the Island. “We have never had a sighting down Island,” Mr. Ben David said.

“This is very likely a canine and people should be on the lookout because it’s in the nature of canines to go back to the scene and do it again. The odds that this was a coyote are almost nil,” Mr. Ben David said.