On December 17, 2011, Bolinas resident Pegan Brooke was walking near Agate Beach when a snarling white pit bull charged her and her Border collie mix, Millie. The pit bull, named Diamond, knocked Millie over and tore a swath of hair and flesh off her back. Brooke jumped in, yelling and jabbing her elbow into Diamond’s face.

Brooke and Millie survived, though both sustained injuries—Millie required two surgical procedures and multiple bouts of antibiotics. “It was very scary just because it was so out of the blue,” Brooke, an artist and professor at the San Francisco Art Institute, said.

In a county hearing earlier this month, Diamond and another dog, a Lab named Cassie who also belonged to Bolinas resident Sue Anne Russum, and who was present during the attack, were deemed “potentially vicious,” meaning they must be confined to Russum’s property.

The judge also ordered that Diamond, who has a record of unprovoked hostility, be euthanized. According to Carrie Harrington, a spokeswoman for the Marin Humane Society, Russum is appealing the ruling.

Diamond, Cassie and a Great Dane mix named Indo, all Russum’s, have been linked to similar attacks dating as far back as 1995. Dozens of complaints of mauled or slaughtered pets have been logged with the Humane Society, the most recent in 2009 when Diamond killed a neighbor’s cat and severely injured a dog. The pit bull was deemed “potentially dangerous,” meaning Russum had to keep her under adult supervision and on a leash with an escape-proof collar whenever they left home.

Dangerous dog designations remain in effect for three years, and additional complaints during that period trigger a “vicious dog” hearing that can lead to fines, further sanctions and euthanization. If a dog attacks a person the owner can face a vicious dog hearing, regardless of the animal’s history.

The latest attack violated Diamond’s 2009 sanctions, but Brooke, despite being shaken, did not intend to pursue a complaint. “Really, I just wanted to pay my vet bills and be done with it,” she said. But Brooke’s doctor was concerned that Diamond might have rabies, and persuaded Brooke to post a sign in town asking for information about the pit bull. Calls began flooding in.

“I would say I got around 30 phone calls from neighbors and other people in town, most of whom I didn’t even know, recalling similar attacks,” Brooke said. “It was shocking.”

Brooke decided to notify the county. “I felt I had a responsibility as a citizen,” she said. “I had no hard feelings toward [Diamond], it just seemed the right thing to do.”

Cassie had been classified as potentially dangerous in 2005 after she and Indo allegedly killed a neighbor’s cat. Both had subsequent violations in 2006 and 2008, but the dogs were never declared vicious because witnesses refused to pursue complaints. Humane Society Captain Cindy Machado said the time it takes to fill out forms and testify often deters witnesses; and as witnesses typically know the aggressors’ owners, they can be intimidated by the prospect of confrontation.

In an interview after the 2009 attack, Machado said Russum’s dogs posed a particularly serious threat: “This is a revolving door. Whatever dog ends up in this household appears to be problematic.”

At the time Russum’s son, Memphis, who was not available for comment this week, agreed to replace the fence under which the dogs had escaped. He said Bolinas had a long history of dogs roaming free and he felt it was unfair to single out their pets. “It’s a dog town out there,” he said. “They do whatever they want.”

Bolinas resident Madeline Muir, who said she saw Russum’s dogs kill a baby deer a few years ago, was heartbroken by the order to put Diamond down. “I feel bad because I know she loves that dog very much,” she said. “I don’t know, what do you do?”

Another Bolinas dog owner who did not wish to be named said he witnessed the dogs’ aggressive behavior while trimming trees once in Russum’s backyard. “I said to the woman, ‘Hey, if you don’t take care of them I’m going to leave.’ And from then on I’ve never gotten a job from her again,” he said. “It’s like a criminal losing their gun and then just going out and getting another one. There was a time when my dog kept barking, so I put him on the ground and just kept telling him to stop. That’s the only way to stop this. That’s what responsibility is all about.”

Harrington said her agency receives very few vicious dog complaints, and when it does it does not handle them lightly. “Not every dog is going to be suitable for parks or beaches,” she said. “Dog guardians need to be mindful of other dogs and people, and remember that they have a responsibility to not only care for their companion animals but for others as well.”