CONCORD — Two Concord roommates are seeking an explanation as to why a police officer shot their aging cocker spaniel during a neighborhood search for a suspicious person last week.

Zach Grimm and Dave Biller say Kirby, a 13-year-old cocker spaniel, is recovering from a gunshot wound to the shoulder after barking at an officer in the backyard of their home in the 2000 block of Weaver Court on June 17.

But a week after the incident, the two say they have received no explanation from police about why officers were in their yard. Worse, they said, they have not received an apology from the department.

“It’s obviously pretty upsetting,” said Grimm, 29, who said the dog has been in his family for about 10 years. “The officer who shot at him, after it was over he just sort of had this goofy look on his face, almost like a smirk, and then he left. No explanation, no apology or anything.”

Police were in the area around 4:30 p.m. after reports that a person posing as a door-to-door salesman was looking into backyards, according to Concord police Lt. Bill Roche said. In the course of the search, officers entered the backyard of the residence and were confronted by the 29-pound, reddish-brown dog.

Accounts of what happened next vary. Grimm and Biller say that Kirby simply barked at the officer “like any dog protecting its home,” Grimm said. Concord police contend that the dog was aggressive enough that the officer perceived a threat and fired once only after a warning was given.

Police would not name the officer who shot the dog but did say that he has previous experience with the city’s animal control unit.

“The officer determined that the dog was posing enough of a threat that he fired a single round to stop the dog,” Roche said.

The department had no other comment. Police did not find the suspicious person.

Grimm and Biller said Kirby has been recovering steadily since the incident. The bullet fragmented as it entered the dog’s body and a piece of it remains lodged by the spine, Biller said.

“But the wounds are healing, so we think he’s going to make it,” Biller said.

“I can’t believe he’s alive, to be honest with you,” Grimm said. “I think he’s trying to figure out what happened to him. He was just doing his thing, protecting his home.”

Contact Rick Hurd at 925-945-4789 and follow him at Twitter.com/3rdERH.