Harley, a yellow Labrador retriever, was kicked to death on Sunday night. Calgary police are investigating. (Courtesy Doug Shields)

Police and the Calgary Humane Society are investigating allegations that an off-duty police officer kicked a dog to death.

Doug Shields and Melanie Dunne say they were working in their yard in the southeast neighbourhood of Lake Bonavista on Sunday night with their dog, Harley, by their side.

When they took his leash off to let him into the house, he saw another dog and darted across Lake Waterton Way S.E.

Harley, a three-year-old yellow Labrador retriever, rounded the corner where a man was walking his dog.

"I watched as the two dogs reached each other and they stopped and they were sniffing each other," Shields told CBC News on Tuesday.

When Shields looked down to step off the curb, he said he heard his dog make a noise.

"The next thing I heard was a yelp. As I looked up, Harley was in distress and he fell into the gutter and within seconds, 30 seconds at most, he was dead."

On Tuesday morning, an off-duty officer, who works in community policing, came forward and said he was trying to protect his pet from an attack by the other dog.

Off-duty officer unaware of dog's injuries

"Our officer advises he was protecting his own dog and took actions to protect his own dog," said acting Deputy Chief Trevor Daroux in a news conference on Tuesday. "I understand that he did say that he did strike the dog."

Daroux commended the officer for coming forward, even though it was almost two days after the incident. He said the officer was unaware of the extent of the dog's injury until he saw a news report on Monday evening.

Flowers were left in front of the Calgary house where Harley, a Labrador retriever, lived. He was kicked to death and police are investigating. (Zulekha Nathoo/CBC)

"There was some conversation between them but he did leave. It's difficult as I said to speculate on why, in an emotionally charged situation, people do what they do but that is something we'll be looking at," said Daroux.

Shields disputes the allegation that Harley was attacking the other dog. "I was within 30 feet of it, I saw this. There was no bite, there was no fight," he said.

But Shields said the man blamed him for not having Harley on a leash.

"I was yelling at him, 'Well, what the hell did you do to my dog?' And he yells back, 'Well, I kicked him. He deserved it, he attacked my dog.'"

Neighbours and strangers have been leaving flowers in front of his southeast home in memory of Harley.

Investigators are looking for witnesses, and police say a necropsy will be done on the dead dog.

Besides police and the humane society, Calgary bylaw services and the Crown prosecutor's officer are also investigating.

No charges have been laid and the officer remains on the job.

With files from Zulekha Nathoo