Brendan Cox, an Alberta government spokesman, said there were reports of another big cat in the area, but they turned out to be false.
"One cougar has been destroyed by officers," he said.
Cox said the wildlife officers had hoped to tranquilize and trap the cougar that was lying in tall grass.
He said after watching the animal they determined the adult male cat was too riled up.
Cougars can become agitated when they get hit with a tranquilizer dart, Cox said, adding the cat could have run into a more populated area, putting people at risk.
"Cougars being very quick and agile pose a high risk to escape the area," he said.
"Our officers had to make a very difficult choice. Ultimately their first priority is public safety."
Cougar sightings in Alberta have become more frequent in recent years as the number of big cats has increased along with the number of deer and elk.
The province says conflicts between people and cougars, which can weigh between 40 and 90 kilograms, are rare.
Alberta Justice said in a statement that the decision to kill the cougar was a difficult one, but was made in the interest of public safety.
(The Canadian Press)Suggest a correction