CALGARY -- There was little choice but to fatally shoot a cougar that had been loitering outside a Calgary hospital Thursday, provincial wildlife officials say.

Wildlife officers shot the cougar about three hours after it was spotted lurking around a stairwell at a nearby construction site before moving on to the grounds of the South Health Campus on the edge of Calgary.

At least two shots were fired at the big cat in tall grass near the hospital's front entrance after officers deemed the situation too dangerous to the public to tranquillize it, Alberta Justice and Solicitor General spokesman Brendan Cox said.

"Officers will always try to remove the animal, they were hoping to immobilize it," he said. "But even if you tranquilize them, they get agitated and there's a good chance they could escape since they're very quick.

"Our officers concluded that tranquilizing it would increase the threat to the public."

Cox said when a cougar is tranqulized, the effects of the drug don't kick in immediately.

"In that time, the cougar could escape," he said. "In this kind of situation their first priority has to be public safety."

Witness Gordon Griffiths said the wildlife officers first tried to tranquilize the animal.

"They did shoot a tranquilizer and it (the cougar) rolled, but then it got up and lunged toward them," Griffiths said. "It didn't pounce at them but it went toward their direction.

One more bad picture of the cougar through binoculars @CTVCalgary@660Newspic.twitter.com/PfU0m9FRbN — Russell K (@CouleeHiker) September 18, 2014

"The only choice they probably had was to put it down."

Initial reports suggested two of the lanky felines may have been in the area, but police could not confirm that.

"We have officers that have eyes on the one cougar, but there hasn't been a sighting of that second cougar for more than an hour," said police Insp. Keith Cain, who figured the two animals could be one and the same.

The hospital was never locked down, though access was restricted at its main south entrance, Alberta Health Services spokesman Bruce Conway said.

"Patient care continued -- patients and staff were re-routed through the north entrance," he said.

Gawkers could be seen at a hospital window snapping photos of the beast as it lay in the grass for more than three hours.

Cain said officers were prepared to shoot the cougar should it threaten humans, but was confident Fish and Wildlife officers would be able to tranquilize it. A graphic video was taken of the shooting.

"We secured the area and wildlife officers moved in and did what they had to do," Cain said two hours later.

Officers could then be seen hauling the animal away in a black bag.

Wildlife sightings of bears, cougars and even bobcats have increased in Calgary since last week's unseasonal snowfall.

Cox said it's not uncommon to see bears moving into urban areas in search of food before heading into winter hibernation.

"Cougars are pretty rare, but not unheard of," he said.