A Calgary police officer shot and killed an agitated dog after residents complained about it running loose and biting a woman on Coventry Drive in the northeast of the city. (CBC)

An officer responding to a call about an agitated dog in northeast Calgary shot and killed the animal as it charged, police say.

Before officers arrived, the dog had bitten a woman on the hand and was running loose around the 1000 block of Coventry Drive near Coverdale Road N.E., officials said.

When the dog charged, the veteran officer fired several shots, killing the animal.

The officer said he had no choice, that the dog took him by surprise by lunging at him so he had to defend himself.

A woman who identified herself as the dog owner's sister told CBC News the dog was a three- or four-year-old Rottweiler.

She said the dog had been in the backyard of her brother's home and they don't know how it got loose.

The dog is usually friendly and probably got lost, couldn't find its way home and became scared and agitated, she said.

The dog owner's children are devastated by the loss of their pet, the woman said. She expressed regret that the dog had bitten somebody.

Nearby schoolchildren were kept indoors for their safety while the dog was loose.

The officer was not hurt. The homicide and internal affairs units are investigating because the incident involved a firearm shot by an officer.

The woman who was bitten was treated by emergency crews at the scene.