Kassandra Allard-Morin is worried she's about to lose her dog, Bruce, forever.

The American Staffordshire terrier mix has been kept at a city pound since Monday when he broke his supposedly 'unbreakable' collar in her yard, attacked and killed a small Pomeranian dog.

“My heart hurts ever since I haven't been able to see him since Monday,” said Allard-Morin.

Earlier this week, the owner of the Pomeranian, Rachelle Coward told CTV News she thinks Bruce should be put down.

“I would, yeah,” she said. “I know it's hard because it's someone else's dog and they probably love that dog to death,” said Coward.

Bruce was a rescue dog himself. Allard-Morin insists her pet is not dangerous, he was simply acting on instinct.

“If there was any doubt in my mind that my dog was a danger to anyone, I would have this dog put down,” she said. “There are other things that could happen where he doesn't have to be put down and he could come back with his family.”

Canine behavioural consultant Susan Jordan says terriers like Bruce have been bred to hunt small animals for generations.

“Dog to dog aggression - which is what this would be termed as - does not correlate to dog to human aggression,” said Jordan. “It's very possible in this case that the dog was already excited. He could have maybe seen a squirrel, or a cat dash across and it's called trigger stacking.”

When Bruce saw the smaller dog, Jordan says he was already instinctually acting as a predator. Jordan says that instinct is something owners need to be aware of -- they need to provide proper training and supervision.

“He was unsupervised on his yard leash and I think the number one thing to take away from this is just never leave your dog unsupervised, ever,” said Allard-Morin.

Allard-Morin and her partner, Thomas Vaughan, are facing charges of having an unlicensed dog, having an animal running at large and an animal attack. Those offences carry fines ranging from $100 to $5000.

“The thought that he might be put down, or might even be stuck in the kennel for months at a time waiting for court dates, breaks my heart,” said Allard-Morin.

The case is in Dartmouth Provincial Court on Jan. 7. Bruce remains locked up in the city pound where Allard-Morin adopted him a year ago.

With files from CTV Atlantic’s Sarah Ritchie.