Police have confirmed an officer discharged a firearm after a situation escalated in a southwest Calgary park Sunday afternoon.

"A man is currently in custody following a firearms incident in Stanley Park," acting Duty Insp. Phil Hoetger said.

"Police attended the scene and located a man who was carrying what appeared to be a handgun, walking between trees near an area where children were playing soccer."

Acting Duty Insp. Phil Hoetger said the suspect was not injured and he hasn't been charged, as of late Sunday. (CBC)

Hoetger said the park had to be evacuated.

"It was a sunny, hot Sunday so the park was very busy with all sorts of people using it."

He wouldn't confirm information about the member who discharged the firearm or the suspect, other than to say the suspect was dressed in black.

Rick Materi heard the shots.

"We were just up at the top of the hill and saw the chopper flying around," he said.

"We heard the chopper saying, 'Get on the ground, we can see you,' and then we heard two gun shots."

Rick Materi heard the shots and saw a man taken into custody. (CBC)

Materi says police told people to clear the area, "and then all of sudden we saw that they had the guy."

Other witnesses, who asked not to be named, have confirmed details of the incident.

The Alberta Serious Incident Response Team tweeted an investigation is underway for "an officer-involved shooting, no injuries."

Investigating <a href="https://twitter.com/CalgaryPolice">@CalgaryPolice</a> officer-involved shooting, no injuries. More information tomorrow. —@ASIRT_AB

Paramedics say they were initially called to the scene, but the call was cancelled as they were not needed.

Police say there were no injuries and the suspect had not been charged as of Sunday evening.